if you are working with a wood that is questionable,, then the rule of thumb draw lengths,, and bow lengths are out the window
,, if you really want the bow to work, then overbuild it,, draw it shorter etc,, if that one works,, then you can try a more aggressive design,, I would start with longer bow, shorter draw, and rawhide back,, sinew back would increase odds of success as well,, i would not go more than 22 inches draw,, and that is rawhide backed,, maybe longer draw with sinew,,