For what it is worth Steve, I put a fillet up the inside corners in lieu of the timber quad and then laid double biased tape over that while it was still very green. I also drilled and epoxied quarter inch dowels through the sides and well into the front face. I have had the unstayed mizzen out in quite a strong blow (28 knot gusts) without any signs of trouble. Still, laying glass over the front face can't be bad, but I wanted mine to have a timber finish.