i have one peice mounts on both my the cfx and big cat. i ran into the same problem with the scope being too far from my eye when the mount's pin is set into th risers stop pin hole, so i decided to not use the stop pin on the mount and moved the scope mount all the way back plush with the end of the riser. the riser is on firm with 4 screws and stop pin holding it, so that wasn't my concern. it's the scope mount that i was worried about, about it sliding off. after i secured it and did some test shooting. the scope didn't creep at all.
i found that aluminium on aluminium grips better than aluminium on steel. so only the riser has to be tightly secured and with use of the stop pin to the gun. if the scope rings or mount is made of aluminium if shouldn't slide.