Smoke 1953, From a pure fps stand-point, on a "glass bow," that you are not pulling past the stack point!!, you will not see much if any speed difference to one made 68" for your 27.5" draw compared to a 70" bow for 29.5" draw that you pull to 27.5" What you might notice, I do, is that with a bow that is too long for your draw has a lot of "wasted limb," and will feel somewhat boingy, or loose at the shot. One made for your draw won't have extra weight out on the limbs needed to make weight compared to the shorter one. Correct bow length for your draw tends to give a taught, solid feel at the short. 27.5" draw go for 67-68" w/backset profile, 66-67" in a string follow profile with 14" risers. If your going to go heavy go with the longer bow.