the one thing you didn't not mention is what you are thinking for points. if you're looking into the carbons to try the increased or extreme FOC...then you 'might' need heavier than the 35/55s as adding a lot of weight to the front end changes the dynamic spine quite a bit.
personally I'm shooting a 56# widow and 58# homemade longbow and I'm, shooting vapor carbonwoods 3000s which are .400 spine (equal to the GT 55/75), with 350 grains up front. 100grain brass insert, 125 grain WW head and 125 grain screw in adaptor. and the .400 spine at 29 inches shoots great out of both bows.
I just ordered GT trads for the first time (today) so I'm gonna have to experiment a little on whether that weight up front is gonna react the same on the different shaft. we'll see.