Here's the lazy man's approach. You can get the bumpers at Home Depot and trim a little with a sharp knife to allow it to stop the trigger right after it releases the hammer. It's hard to say if it helps. Mine occasionally fall off when the adhesive succumbs to cleaning solvents. When that happens, my accuracy doesn't change enough to notice.
However, I have been shooting this P-11 with a P-40 conversion long enough that I may no longer need it. It seemed to help me when I first installed it.
Lot's of gun gadgets are like that. Eventually, your experience level makes them less important. I guess that's what practice is all about. 8)