If it's a newer 77 with the larger loading port you've got more options. If it's an early one with the narrower loading port it's all about getting your fingers in to load up. Similarly the mk1 stocks have a lower cheek piece so that makes lower mounts more comfortable.

My sig picture (below) has a Bushnell Elite 3200 10x40mm with high (I think?) mounts, but that's because of the small port and the high cheekpiece. If I switch to the mk1 stock I reduce the mounts.