I put a micrometer depth gauge on the GG holder and noted that the depth was already almost too deep to meet spec, so I removed the fresnel screen and put it on the smooth outside of the ground glass screen. If it scratches too much, it's easy enough to replace. What I did notice is that the GG frame corners needed to be routed out a bit to allow the GG to sit accurately and flat on the frame. The fresnel does definitely help illumination very noticeably and is worth retaining so long as it does not interfere with accurate focus.

Thank you to everyone for your kind suggestions.