Beavertail-installation jigs take a lot of the guesswork out of reshaping the tangs, while quelling the anxiety of removing too much metal. But I soon found out my concern was misplaced. It turns out when it's really easy for your file to skid off course while filling metal, which results in your work being be speckled by dings and pockmarks flanking the backstrap. Luckily, Kuleck and Oldham discuss this disheartening dilemma in their book, so when madam misfortune visited me I was prepared.
Whether you chose to remove the beavertail or leave it in is a matter of preference. Start with a half-round, smooth file and use it to blend each side of the backstrap inward. Afterward, I repeated the process with a set of jeweler's files prior to switching over to emery cloth, and then progressively finer grits of wet-or-dry sandpaper. (I started at 400 grit and stopped at 2,000 grit.) The book describes using it like a shoeshine rag across the width of the backstrap. It took some time, but eventually the gun's gouges were gone.