Pau amerillo or yellowheart is fantastic belly wood. Very elastic stuff, density around 0.65 - 0.7, soft in an easy to work way and sands/finishes very nicely. I really rate it.
It will do a hundred pounder no worries. The heaviest bow i've made from it was 87# from memory, it was an elb only a shade over 1 inch wide at the handle, kept that width for 8 inches either side of the handle tapered to 11/16th 8 inches from the nocks down to just over 3/8ths.
Pearl - true yellowheart is very different to ipe you must have had something else.