Just a small observation in the range of spine needed for our bows, and how hard it is to evaluate this online without actually going out and shooting. I have two Hummingbird Kingfisher longbows, 53# (66") and 52# (60"). The 53# bareshafts perfectly with a 31.5" Traditional Only 400 spine with a 160-grain point. The 52# shoots best with a 31.5" 500 spine Traditional Only with 190 grain-point. Everything else on these bows are set up the same (plate material, rests, strings, silencers, etc), but they need vastly different arrows to shoot right. Just goes to show you how that 1 pound difference in draw weight (coupled with the natural variation in bows even from the same bowyer) can really affect your setup.
Probably the 4" of extra bow length may change the power stroke.
Bow length probably affects your release as well.
Good point though--don't take anything for granted when tuning.