RE: bowtech limbs
I wouldn' t see a problem with shooting that bow at 60-64 lbs, and if it is more comfortable or happens to bring the spine in perfect for you that' s what I would do. I don' t buy into the whole thing about a bow being more efficient (by any significant amount) with the limbs cranked down than one with heavy limbs backed off ten lbs. There may be a tiny difference and I don' t claim that I can prove it. I think the limbs store the energy you put into them- period. If it' s 60 lbs than it' s 60 lbs, reguardless of what limbs it has. The differences might be a small change in limb geometry having a tiny effect on brace height or maybe it has less vibration cranked tight.
I think you bought the right limbs if you are comfortable shooting anywhere between 60 and 70 lbs., but that' s just my opinion.
-Chief