By D bow I assume you mean a stiff handled bow.
For 50# to 60# @ 28" you could go 1 1/4 to 1 1/2" wide to midlimb than taper to 1/2" nocks. Roughly 8" of handle section including 4" fades, 2" on upper and lower. If the area where the handle will be is less than say 1 1/4" thick, or deep, you could flatten it off before you start and glue a couple of 1/8" slats there, say a 10" and 8", then shape that into the fades and handle. Better to use muilitple thin pieces, plenty long, than a single, short thick piece which will almost certainly pop off, depending.