If you guys have male mulberry, it is way lighter than the females.  They grow nice and straight and get really big, but the wood of the males where I live are only .50 sg.  Some of the females are mid to high 60's sg, but usually pretty gnarly.  The males will make a fine bow, but it takes a lot more of the wood to do it.  I usually build em 2" at the fades to midlimb on flat bows and add two inches of length per limb for male mulberry.  With females, I build em 1 3/4 " fade to midlimb normal length.  Even at those blown out proportions, the males will start coming into floor tiller (just starting to bend) while they're still 3/4" thick.  The difference between male and female mulberry is pretty profound.  I can't think of any other wood that I've used that is that different.  Anyway, that's What I've experienced with mulberry.  I hope it helps.  Josh