I'll start you off with a few ideas.
I've only made a few and,they broke. So this is what I learned.
Make the limbs wide , I'd start with 2 inches. Either use a true pyramid shape or go part way down the limb then taper,to,about 5/8 inch tips to start.
Leave it long till you decide to keep the length or shorten it to help make weight.
Handle, on my bows I figure 4 inches for my hand then 2 inches on each side for fades.
The actual,width at the handle from 1 to 1 1/4'inches.
I'd suggest doing a,search of the build a longs for additional info.
Hopefully some more experienced self bow,guys will add to or correct my numbers.
It is,difficult to get,a,real formula since,all,wood is,different.