i was about to say you should try the stabilize node instead of the matchmove as it seems to have fewer bugs, but checking your numbers the shake globals seem to be weird indeed.
here are some manually calculated numbers:
square PAL: 768x576
unsquare PAL: 720x576
--> aspect ratio: 0.9375 or 1.0667 (depending how you count)
shake globals: 0.914077 !?? -> factor 1.0256 off)
square 16:9 PAL: 1024x576
unsquare 16:9 PAL: 720x576
--> aspect ratio: 0.703125 or 1.4222
shake globals: 0.685401 !?? -> factor 1.0259 off)
i'm sure there is a reason for this 1.025.. difference, but i frankly i have no idea what it could be 
so personally i'd stick with 0.703125
below a quick test i did which seems to work perfectly fine, but of course there's no "real" 16:9 anamorph footage in there so the difference above cancels itself out.
hope tha helps
++ chris
CODE
Checker1 = Checker(720, 576, 1, 50, xSize/GetDefaultAspect());
Color2 = Color(720, 576, 1, 1, 0, 0, 1, 0);
Move2D1 = Move2D(Color2, -134.0562, -67.2113, 0, 0.685400963,
0.4211075, 0.242098466, 0, 0, 360, 288, "default", xFilter,
"trsx", 0, 0, 0.5, 0, 0, time);
Move2D2 = Move2D(Checker1, Hermite(0,[-225.14,96.96,96.96]@1,[276.568,96.96,96.96]@25),
Hermite(0,[-212,92.96,92.96]@1,[4,92.96,92.96]@25), Hermite(0,[0,83.41,83.41]@1,[90,83.41,83.41]@25),
0.685400963, Hermite(0,[1,-1.58,-1.58]@1,[0.4027,-1.58,-1.58]@25),
Hermite(0,[1,-1.58,-1.58]@1,[0.4027,-1.58,-1.58]@25), 0,
0, Hermite(0,[360,0,0]@1,[360,0,0]@25), Hermite(0,[288,0,0]@1,[288,0,0]@25),
"default", xFilter, "trsx", 0, 0, 0.5, 0, 0, time);
MatchMove1 = MatchMove(Color2, Move2D2, 1, "4 point", Tracker1.track1X,
Tracker1.track1Y, 1, 1, Tracker1.track2X, Tracker1.track2Y,
1, 1, Tracker1.track3X, Tracker1.track3Y, Tracker1.track4X,
Tracker1.track4Y, 0, 0, Background.width, 0, Background.width,
Background.height, 0, Background.height, "default", xFilter,
0, 0.5, 0, 1, "Over", 1, "v2.0", 1, 0, 0.685400963, 18, "1/64",
"luminance", 0.3, 0.59, 0.11, 0.75, "use start frame", 0.5,
"stop", 0, 0, 25, "track1", 424.462-height/25, 424.462+height/25,
196.438-height/25, 196.438+height/25, 424.462-height/15,
424.462+height/15, 196.438-height/15, 196.438+height/15,
"track2", 517.082-height/25, 517.082+height/25, 423.797-height/25,
423.797+height/25, 517.082-height/15, 517.082+height/15,
423.797-height/15, 423.797+height/15, "track3", 464.473-height/25,
464.473+height/25, 467.812-height/25, 467.812+height/25,
464.473-height/15, 464.473+height/15, 467.812-height/15,
467.812+height/15, "track4", 375.159-height/25, 375.159+height/25,
238.266-height/25, 238.266+height/25, 375.159-height/15,
375.159+height/15, 238.266-height/15, 238.266+height/15);
Stabilize1 = Stabilize(Move2D1, 1, 1, "4 point", Tracker1.track1X,
Tracker1.track1Y, 1, 1, Tracker1.track2X, Tracker1.track2Y,
0, 0, Tracker1.track3X, Tracker1.track3Y, Tracker1.track4X,
Tracker1.track4Y, "default", xFilter, "trsx", 0, 0.5, 0,
1, 1, 0, 0.685400963, "v2.0", 18, "1/64", "luminance", 0.3,
0.59, 0.11, 0.75, "use start frame", 0.5, "stop", 0, 0, 25,
"track1", 424.462-height/25, 424.462+height/25, 196.438-height/25,
196.438+height/25, 424.462-height/15, 424.462+height/15,
196.438-height/15, 196.438+height/15, "track2", 517.082-height/25,
517.082+height/25, 423.797-height/25, 423.797+height/25,
517.082-height/15, 517.082+height/15, 423.797-height/15,
423.797+height/15, "track3", 464.473-height/25, 464.473+height/25,
467.812-height/25, 467.812+height/25, 464.473-height/15,
464.473+height/15, 467.812-height/15, 467.812+height/15,
"track4", 375.159-height/25, 375.159+height/25, 238.266-height/25,
238.266+height/25, 375.159-height/15, 375.159+height/15,
238.266-height/15, 238.266+height/15);
Tracker1 = Tracker(Move2D2, "1-25", "1/128", "luminance", 0.75,
"update every frame", 0.5, "stop", 1, 17, "v2.0", 0.3, 0.59,
0.11, 1, 10, "track1", Linear(0,74.5104@1,93.3004@2,114.347@3,133.411@4,154.716@5,175.279@6,193.515@7,217.679@8,238.774@9,259.502@10,283.881@11,307.944@12,331.248@13,355.237@14,376.484@15,400.473@16,424.462@17),
Linear(0,146.938@1,149.219@2,150.86@3,152.954@4,152.196@5,156.196@6,160.813@7,161.875@8,164.547@9,169.531@10,169.281@11,173.438@12,176.438@13,183.438@14,184.438@15,189.438@16,196.438@17),
Linear(0,0.5317@1,0.529@2,0.897@3,0.9949@4,0.9128@5,0.1696@6,0.993@7,0.9618@8,0.9564@9,0.953@10,0.9538@11,0.5099@12,0.4379@13,0@14,0@15,0@16,0@17),
409.600677, 435.206573, 174.669647, 209.736359, 400.224762,
444.582428, 162.469681, 221.936325, Linear(0,74.5104@1,93.3004@2,114.347@3,133.411@4,154.717@5,175.279@6,193.514@7,217.678@8,238.774@9,259.502@10,283.881@11,307.944@12,331.248@13,355.237@14,376.484@15,400.473@16,424.463@17),
Linear(0,146.938@1,149.219@2,150.86@3,152.954@4,152.196@5,156.196@6,160.813@7,161.875@8,164.547@9,169.531@10,169.281@11,173.438@12,176.438@13,183.438@14,184.438@15,189.438@16,196.438@17),
1, 1, "track2", Linear(0,373.45@1,387.158@2,396.754@3,407.678@4,415.405@5,424.105@6,433.663@7,441.816@8,448.893@9,455.939@10,464.45@11,471.667@12,480.973@13,489.889@14,496.595@15,506.994@16,517.082@17),
Linear(0,145.992@1,171.992@2,202.992@3,228.984@4,251.984@5,276.984@6,295.984@7,317.438@8,336.297@9,352.828@10,366.797@11,381.703@12,391.656@13,403.297@14,409.578@15,418.766@16,423.797@17),
Linear(0,0.7617@1,0.3878@2,0@3,0.6468@4,0.7249@5,0.7279@6,0.7985@7,0.9635@8,0.9597@9,0.9583@10,0.9598@11,0.9586@12,0.9536@13,0.9492@14,0.9461@15,0.9321@16,0.94@17),
502.7465, 525.1539, 403.165344, 434.898682, 487.658936, 540.2414,
385.632019, 452.432, Linear(0,373.451@1,387.158@2,396.753@3,407.677@4,415.405@5,424.106@6,433.663@7,441.816@8,448.893@9,455.939@10,464.45@11,471.667@12,480.973@13,489.889@14,496.595@15,506.994@16,517.082@17),
Linear(0,145.992@1,171.992@2,202.992@3,228.984@4,251.984@5,276.984@6,295.984@7,317.438@8,336.297@9,352.828@10,366.797@11,381.703@12,391.656@13,403.297@14,409.578@15,418.766@16,423.797@17),
1, 1, "track3", Linear(0,374.207@1,381.412@2,384.277@3,388.584@4,393.6@5,397.112@6,401.205@7,403.866@8,408.712@9,415.071@10,418.548@11,424.66@12,431.07@13,438.775@14,446.217@15,454.596@16,464.473@17),
Linear(0,291.516@1,316.508@2,338.508@3,360.508@4,377.438@5,399.313@6,411.313@7,425.172@8,435.297@9,443.984@10,452.141@11,457.844@12,462.266@13,466.984@14,468.891@15,467.781@16,467.812@17),
Linear(0,0.8808@1,0.7399@2,0.8701@3,0.9701@4,0.9951@5,0.995@6,0.9944@7,0.9647@8,0.9612@9,0.9595@10,0.9559@11,0.9511@12,0.947@13,0.9393@14,0.9488@15,0.946@16,0.9478@17),
450.165, 473.9432, 448.24234, 481.975677, 438.961426, 485.1468,
429.709, 500.509, Linear(0,374.207@1,381.411@2,384.277@3,388.584@4,393.6@5,397.112@6,401.206@7,403.866@8,408.712@9,415.071@10,418.548@11,424.66@12,431.07@13,438.775@14,446.217@15,454.596@16,464.473@17),
Linear(0,291.516@1,316.508@2,338.508@3,360.508@4,377.438@5,399.313@6,411.313@7,425.172@8,435.297@9,443.984@10,452.141@11,457.844@12,462.266@13,466.984@14,468.891@15,467.781@16,467.812@17),
1, 1, "track4", Linear(0,73.8696@1,86.918@2,101.715@3,115.828@4,131.609@5,146.907@6,164.042@7,183.27@8,201.565@9,221.48@10,239.67@11,261.195@12,282.937@13,305.364@14,327.105@15,351.17@16,375.159@17),
Linear(0,292.446@1,288.485@2,284.298@3,282.798@4,278.626@5,274.704@6,270.704@7,265.625@8,260.594@9,256.594@10,254.578@11,251.672@12,248.375@13,247.5@14,241.328@15,240.266@16,238.266@17),
Linear(0,0.9556@1,0.9276@2,0.8809@3,0.8543@4,0.986@5,0.8679@6,0.4991@7,0.9592@8,0.9566@9,0.9522@10,0.9457@11,0.9462@12,0.9218@13,0.8687@14,0.7857@15,0.6404@16,0.4322@17),
357.203522, 386.0079, 221.252, 251.652023, 347.370667, 395.840729,
206.385361, 266.518616, Linear(0,73.8696@1,86.918@2,101.715@3,115.828@4,131.609@5,146.907@6,164.043@7,183.27@8,201.565@9,221.48@10,239.67@11,261.195@12,282.937@13,305.364@14,327.105@15,351.17@16,375.159@17),
Linear(0,292.446@1,288.485@2,284.298@3,282.798@4,278.626@5,274.704@6,270.704@7,265.625@8,260.594@9,256.594@10,254.578@11,251.672@12,248.375@13,247.5@14,241.328@15,240.266@16,238.266@17),
1, 1);
Over1 = Over(Stabilize1, Move2D2, 1, 0, 0);