Unlike a rifle where getting taller than required rings interferes with your check-to-stock weld, taller rings on a handgun really don't affect anything. They do, however, allow you to get your thumb underneath the scope bell to pull the hammer back. I don't know about your XVR, but on an Encore pistol that scope to hammer gap can get kind of tight for your thumb.
^^^This. If your XVR is like mine and has the integrated Picatinny rail on the barrel, and you're not using a frame mounted base, the scope will probably be mounted far enough forward that it does not interfere with access to the hammer. Ring height would then be determined by the size of the bell on the scope. If you are using a variable scope, it's nice to have more height for easier access to turning the zoom. When I had the 2X on mine, I used Medium height rings. I suggest you call(1-800-683-5590) Warne or go to their website and use their "technical support" page. They have always been more than accommodating for me whenever I had a question.