Well, how thick are they?
The plan needs to be to glue up the backed blank as close to finished thickness as possible so you don't scrape away all your osage, right? Trust me, I've done that 2 dozen times with different stiff woods like ipe or black locust, ending up with barely 1/8" on the belly.
I find that, as a starting point, if I have about 1-1/2" width, some Perry reflex or R/D, and lengths around 66-70" or so, the "stack" off the form rarely needs to be thicker than 1/2" midlimb. Thicker only for low-stiffness wood like ERC (I assume yew?) or if you absolutely want to work fades down out of a handle. I purposely cut any good belly wood I come to the fat side of 3/8" thick, and count on adding a powerlam. Then a 1/8"-3/16" thick backing and I'm good.
That also means your maple backing MAY need to be quite thin, so it will need to be the best quality wood and best grain you can find for a backing. Lastly, back to basics from the TBB, if you are worried for some reason, add width if you can. Nothing wrong with a 1-3/4" to 2" limb base on an osage bow, if you have the wood. You can always narrow later.