Hi!
The Ca glue metod is no good! Its messy and the surface gets to hard.
A much better metod is to just lay out several layers 25g glass Weave (or 105g satin weave) on the center section, shaped to a diamond form for strongest and stiffest structure, and then pour on some 24 or 30 hour epoxy, spread out with SIG plastic spreader or soft brush.
No contact spray is needed or should be used. When the epoxy has dried after one or two days it's hard but easily sanded with 240 paper. Oracover plastic film is then easily fastened to the glass surface.