Do it, but be sure to wear your kevlar bodysuit to avoid getting skewered when it breaks.

Honestly, I think if you're going so far as to layup a fiberglass frame, you might as well get CF and an appropriate epoxy and do a CF frame. If you look around, there's info out there on how to do this. I think Sheldon's site has an article from a guy documenting his frame building escapades.

Of course I've never worked with fiberglass or CF.