The most efficient bow in the TBB bow contest was 76" long if I recall. In my experience with 150+ wood bows, Shorter bows compress belly wood, leading to more string follow, and lower performance, not to mention instability and string pinch. I have shortened several bows from 68" to 66", increasing their draw weight by 2-3lbs, only to find out when I shot them over a chronograph, that they shot exactly the same speed as before, I just had to pull harder to get there! Longer bows are also more inherently stable, and not really a hinderance anywhere except a tree stand. If I was you, I would build a 72" or longer bow with 6 inch stiff tips. See how you like to shoot it, and if you want more weight or less length, shorten it two inches and try again.