I think it might be ok, but who really knows until you try.
Honestly if your tiller is perfect you're probably Ok, but if not then ..... BOOM!
I also think it can depend what you're backing. If you were backing walnut, then I'd say hickory is sooooo much stronger it probably won't matter, but Ipe is a rare bird in that it is so ridiculously strong.
That backing strip is not ok for a highly stressed design (I.e. Trapped back, reflex, long draw, high draw weight, narrow limbs etc.)
I'd make it as long and wide as you can, don't glue the bow up with more than a hair of reflex, and tiller carefully to a moderate weight like 45# if you're set on using it.