The rails are only screwed with 0 slope. Built that way so you can remove the rail and spin it 180 degrees to get a different position on the slots, obviously for eye relief adjustments.
No options that I know of from AI, but there are a few custom makers for bases. The only I can remember at the moment is,
You could put an aftermarket Ken Farrell rail on and add 20 MOA, but why? The replacement rail runs $110, and then you're still going to be spending money on the rings. The AI picatinny mount is a one-piece design, adds 18 MOA, and retails for $195:
You wind up spending your money on a mount that you can pull off and use on other platforms as well, rather than a rail that's going to stay on the one rifle only...it just makes more sense that way.