You have 3 solutions:
1) take the <R, U> scrambler and just treat R as M (in your mind).
2) Modify the source code to add another scrambler (just copy the R U one and turn it into M U one)
3) Modify the R U one into a M U one completely which should be easier than adding another one.
I ended up realizing that with the added M support for importing scrambles I can just generate a ton from another source and import them.
