MSP,
I have made several Maple bows lately, draw in excess of 70# (sent to other PA members) and I backed all of those with thin pieces (1/8" or less) of plain sawed & straight grained black walnut. I used Titebond II (just cause thats what I allways use). Haven't had any tension failures at all. Just keep the walnut thin or youre in for some more tillering.
I flatten and smooth both surfaces, use a hacksaw blade for a toothing plane, spread the glue to both surfaces with my finger, wrap the whole deal in stretch wrap (makes good glue joint edges) , wrap it all up with rubber bands-surgical tube-or such and set aside for at least 12hours....then unwrap and let the glue cure some more for another 12 hours.......shape and yer done. Maple with black walnut backing has been real good to me ever since I first tried it.
I'm sure other guys have better advice but this is what I use a lot of.....hope it helps ya out some.
rich