I agree with Pat on the belly selection.
I never built an ASL so I’m not sure if there’s certain dimensions you should follow. Just some rough guidelines that work well for a lot of tri lams designs:
1 3/8” at the fades for 6” then taper to 1/2” tips. 3/16” core with a taper, 1/4” belly, 1/8” backing.
You’ll have to dial in your recipe as you build a few.
I’m confused by the bamboo drum sander comment. I use bamboo for my tri lams and I don’t have a dum sander. You use the outside of the bamboo for a backing, not the inside like you would if you were making bamboo lams.