Hopefully someone will come along who has more experience than me with boo backings, but basically, you need big boo. Like 5-6" diameter stuff. With smaller boo, there's a lot of crown, which tends to keep the boo too thick in the center, overpowering the belly wood. I think Rich Saffold uses fairly small-diameter black boo to make some nice bows, but he usually makes really narrow ipe/boo bows an inch or less wide. Just split the boo, cut it to shape, and flatten the inside until it's about 1/8" thick in the center with knife edges. Some people taper the boo in thickness from handle to nocks, some don't. and yep, I've seen some nice all-boo bows posted here.
