Carbon arrows always gave me the fits, so many people have them figured out, not me. But I will say that a 3555 should be real good place to start. 75's should be pretty stiff (skipping right over the 5575's). Carbon is funky with length though, but even still - 50#-ish lbs, 28" arrow, 7595, 275 up front still seems stiff. Are you sure you did the calc data right? My grizzly is 55# @ 28, I draw 27", I shoot 29" 55-60 surewoods with 160 grain tips. Arrows fly wonderful, and sit right at 500 grains. Id take another look at the 3555's, theyre a very universal shaft for the common draw weight range. Just my opinion though.