c-cat

Start lighter with lighter weight. If 2oz. is matt peel it in half for first lam on tooling gel. Then lam another 2oz. After which you can use heavier mat'l. Lighter at first helps to eliminate print through of fiberglass weave to the parts. If your building a production intended mold you may wan't to search silica sand core in the composites and repair section (aircraft). Iv'e used the method in the past with real good results. Super stiff tooling that won't deform or sag.