A trilam with ipé on the belly can get really thin. A 1/8" core and 5/32" backing might be a bit thick, but depends on the width of the bow. A narrow longbow of, say, 1" wide at the handle will still contain enough ipé in the end. But a wider flatbow...might end up with very little ipé near the tips. The best advice I can give you, is to always taper the backing AND core a bit when making a trilam with ipé belly. Use a belt sander to thin the last 20" of each lam (each end) about 1/16" or so. That'll give just a little more ipé near the tips, and looks better as well.