Cap.,
I agree with the other members about not filing on the mag release - BUT - why not call Maria at Rohrbaugh and see about buying an extra release. (Even though the release isn't on the list of 'regular' spare parts like springs and grip screws, Rohrbaugh has been pretty good about selling me various internal bits.)
Then you can find a gunsmith to serrate it for you or you can buy a checkering file from Brownell's or Midway and do it yourself. If you've done any hobby gunsmithing and have a selection of drift punches, it isn't too hard to switch out the mag release without sending the hammer spring to the dark place under the furnace where all freed small parts seem to go!
I respect the opinion of the members who wish to keep their R9 pistols pristine, but I've always felt changes that make a gun, or engine, or whatever, work better for me are good things. As long as I can go back to the stock set-up.
Good luck and let us know how you make out. You've got me thinking about serrating my mag release, but my Dad always told me to practice on the other guy's stuff first....
Steve