I have been using my Caldwell Rock BR rest to shoot 30 yard challenge targets and made a modification others might find of interest. I'm using hunting type guns that are light with narrow fore ends that don't interface with the rest well. My first change was to cast up a 5lb block of lead 3 inches wide and a little over 3.5 inches long. I attached it where the picatinny rail was using longer #8x32 screws (I'll include a picture). It works but seems overly heavy and doesn't go on or off quickly. Then I cast a 2.5 lb block which also works and seems heavy enough but it's height isn't great for the rest and it still doesn't go on or off quickly. So I made a wood block that clamps to the picatinny rail with two screws and more than doubles the height. Turning the two screws less than a full turn allows it to go on or off. So quick on and off. I've only sighted in a scope with it so far but it seems to work great.