My P2 came with a BrightScreen glass and a fresnel. I wanted to try an OEM Sinar GG because I like the grid pattern better. The BrightScreen glass is clear with a fresnel installed. The OEM Sinar GG is frosted. So, if I want to use the Sinar GG do I keep or remove the fresnel and if removed, won't I need to shim the Sinar GG?

Thanks,