You are not alone. Already done mine and will be doing a little more.
Glad to hear someone else has an issue with those nasty corners...that don't really need to be there. I did not come close to touching the metal of the mag body in my filing of the corners. I see no valid reason for the current design. Guess it's been that way since the introduction of the RAMI though...2004 if I recall.
Perhaps when CZ's mold for those parts finally wears out they will make a similar modification to the base. I know that it is easier to add material to a part that is injection molded vs taking it away...May as well wait till they need to replace their molds, but I guess if no one is complaining... I mean over 100 views of my post before someone cared to respond in a like minded post. Though from reading this forum for awhile that seems to be par for the course...far more "lurkers" than posters it appears.
Also want to make a similar mod to my Kadet mags but haven't done so yet. Seems a bit more "sacrilegious" to do that to the Kadet..
Happy modding !