If you are looking to increase performance of your selfbow there are better options than backing with glass. The chance of overpowering the belly are too great with just using a glass back. All bow woods are stronger in tension than compression so a glass belly would be more appropriate but I still wouldn't do it. It just isn't necessary.
I know a few bowyers(I believe Dryad, James Parker, et al) that tried a few years ago using glass backs on their "selfbows" but abandoned the idea because of overpowering problems. If boo can overpower bow wood and it has some stretch then you can imagine how glass, with no stretch will be.