If you have a small 60° triangle file, it’s not too much work to mill the minor size through with a small end mill, then file the rest to fit. I’ve done it with sights and slide rackers.
I’ve experimented with this too. What I noticed was that if I literally squeeze my support hand fingers between the thumb (on the rest) and index finger (under the trigger guard) I can create a lot of muscular tension with my support hand and it helps with keeping the pistol flat during recoil.