Most likely I would say yes, and I have thought about making a jig or something to do it. the fact that all the other (non R54) FastTrack pieces hold the rail down without making contact with the flange would make me think there is enough material there to make it work.
It is a lot of time consuming work, and if you grind off to much that could be an issue, and you would have to touch up every spot you grind down with paint to make it blend in.
Ben