Firebird, I would try to refrain from making a part simply out of mat, as mat needs backed with cloth for strength. If mat only is used and the part is stressed its going to be prone to cracking. I always back my mat with cloth on the backside and not the little thin cloth you find at the auto parts store, I head to a boat repair or a fiberglass supplier and get both heavyweight mat & cloth. The way a body is made is in reverse, a gel coat is sprayed into a mold, then a few layers of mat is applied, its saturated with resin and the air bubbles are worked out, tear you mat don't cut it as a sharp line doesn't saturate very well. After the mat is put on the gel coat the cloth is cut and layered over the mat for strength, and it is saturated with resin, the strength is in layers. Unfortuantely when repairing or making small pieces we don't have a mold and we don't use gel coat so we go a little backwards we skim coat the mat with bondo and smooth it out for paint. I have cloth I purchased that has mat on one side already saving a step. I think we have all had the non cure part before, Rogers method might be worth a try as I generally scrape it out, old resin sometimes seems to do this. I have never used the epoxy resins but the nice thing I don't think they dissolve foam but I see it can't be used on some mat?? check out the fiberglasssupply web site for supplies, great prices. I found some really great videos on youtube for fiberglass work, nice tips also. My best tip is use safety glasses with the mekp, I read somewhere if it gets in your eye you have only a few minutes before permanant blindness (found that out after using it several years!)