1.5" might be slightly too narrow to push it beyond 100lb, but I've never worked black cherry. I'd have been inclined to make it around 40 or 42mm wide, get it braced nice and early and see what the wood tells you to do as you monitor set and shape. 40mm is my personal minimum with something like ash when going much over 100lb, and I don't think cherry is quite as forgiving as ash, so wider is better.
As it stands, aim for something like 90lb and keep it full length. If you get it tillered to 90 or so, you can then chop it down to about 78" (if the tiller of the bow and the set allows it) and you'll bump it up by about 10-15lb.