sounds like a nice bow in the making, you have the option of keeping the belly semi flat or flat if you like that design,,
any efficiency advantage of one over the other is debatable ,,,my rounded belly bows did seem to loose a bit more weight in break in ,,, but thats just my experience and others may differ,, also I did make the osage long bows with the round belly a little shorter than I had thought,, they had better cast and less hand shock,,