It looks like the inside of the boo is the belly. IIRC, Tim Baker said it should be the other way around. Yet I read a recent post about how the soft inside can make some scary, but probably harmless noises, as a non-working back. I wonder if it really makes a difference, or one that is negligible. I dont recall, but Tim's reason might have been that wood (perhaps even boo) is generally weaker in compressive strength. But if the inside is essentially useless, what difference would it make, the outside of the boo does both the compressive and tensile work. Of couse the cure and node could make a difference. It might also be possible that the inside is useless for tension, demonstrated by the scary noises, but add a marginal compressive benefit.