My take = fallaway rests when setup properly eliminate fletching contact issues , they may allso make your bow MORE critical of spine and not LESS as they offer less suport to the arrow . This issue allso makes them More critical of nock travel . As far as brace height goes , a short brace bow is a short brace bow and , a long brace bow is a long brace bow . I belive you will be more accurate with a long brace bow [especialy if you have a longer draw length] with a prong type rest [without serious fletch contact] than you will be with a short brace bow with a fallaway . I believe it has more to do with the geometry of where the arrow is in relation to the pivot point of bowhand and grip at the time the arrow leaves the string, than the duration of time the arrow is on the string .