Jeff might not be how your thinking, but all but one of the bows I backed with snake skins I got the most of of them by just using one snake. I cut them in half usually getting two skins between 15" to 19". I start around the fades and it usually takes me close to the static tips. I have wrapped the ends with tread, but the last one I did I kind of made a distressed look by lightly filing the ends in a irregular pattern. I really like that look.
If you want to use the belly and the back of snake separately, I think it would work best to split your snake by cutting up its side between back and belly patterns. Then scrap and dry and split it again on opposite side. Not sure if your snake is wide enough for that, just my 2c worth. Always looking to use what nature gave us to the most we can get from it.
Bjrogg