Has anyone been able to get a Grip Force Adapter to fit a Glock 21SF? Or a Gen 4 G21? Did you have to modify it, or were you able to get it installed without modifications? I ask, because I'm considering ordering one to put on my G21 Gen 4, provided it'll fit. I figure that if it'll fit a G21SF, it'll fit a G21 Gen 4, beings they're the same in terms of grip size.