Think about it! Going from a 68" bow to a 64" bow is only 2" off each end. Will 2" really make that much difference for clearance?? As said, going to a more R/D bow can get you a shorter bow for a given draw length but again, if 2 or even 3" makes that much difference in clearance in a blind/tree stand/etc. you probably need to re-think your setup anyway. Guess what I'm trying to say is that if one end of your bow is 2" shorter, that is not much room to maneuver anyway. You only have 2" of clearance.
Arne