There should be 55 MOA of cant available in the Signature rings, and if you are only using 20 MOA inserts, there is enough to maximize the scope with only the 20 MOA rail he has.

I think my old Zeiss V4 Conquest 4-16 has 110 MOA of travel, and it is a 30 MM tube. While it isn't my favorite scope, i have taken it to almost 1500 yards. There are plenty of scopes out there with 90 moa or more of total travel in a 30mm tube. I haven't used one, but the Athalon Midas Tac 6-24 has 90. For 1000 yards you don't need a huge amount of magnification