The Thompson brothers wrote about using it, irrc. Specific gravity seems to be around .45..which is kind of light for a bow. I'd default to a wide limbed, flatbow design on it, or @70-74" inch long D (a (bend-through-the-handle) bow. I'd be more inclined to make a long D bow.
The wood is a apparently weak in tension, so a rawhide backing may be in order.
I've never tried sassafras. If I had a log, I'd make the first bow @45# to see how it behaves, and then judge from there how heavy I could make the other staves I got from that log.