As far as I know, FX has never made a 20 MOA scope rail for the Maverick that bolted flush to the top posts of the gun. The 20 MOA rails put tension on the top posts that try to move one post up and the other post down relative to the clamping part of the posts that go around the air tube. FX Mavericks depend on things being bolted flush to the gun at right angles so that the structural integrity is sound and stable with rectangular support.
The old FX ZERO MOA scope rails DO bolt flush to the top posts of the gun, as they should. I've known this for a long time, but I don't think I've ever mentioned it before. So if you have an old Maverick ZERO MOA scope rail, use it.
If you find that you need more elevation from your scope, then solve that problem without using the FX 20 MOA scope rail. Maybe get some articulated scope rings or something.
stovepipe
The old FX ZERO MOA scope rails DO bolt flush to the top posts of the gun, as they should. I've known this for a long time, but I don't think I've ever mentioned it before. So if you have an old Maverick ZERO MOA scope rail, use it.
If you find that you need more elevation from your scope, then solve that problem without using the FX 20 MOA scope rail. Maybe get some articulated scope rings or something.
stovepipe