Hey Sir,
I've seem a few Huisache bows on the net.
Haven't built one yet.
But I collected about 10 or 12 saplings last October to give it a go.
Peeled and sealed about half of them so far.
Have done some carving in Huisache, the wood is quite dense, loves the scraper and will produce a fine finish.
Color of the stuff I've got, the heart wood tends to a deep red/brown, but not as dark as Mesquite.
-gus