AR plate is pricey and not, in my opinion, needed for pistol calibres and eventually fail if shot enough with hv rifles. Standard a-36 will hold up to pistols if the plate has any thickness and there is all kind of metal out there, harder than a-36 but cheaper than AR. The best way I believe to suspend a plate is with a stand that absorbs part of the enery and keeps the plate at a slight downward angle. All the good hits will splatter on the ground just behind the target. And yes, do not shoot at cratered plates at handgun distances and always use eye protection. As for size, I use what is available. I sawed some plates out of alloy bar that are 8" and 15" or used 1" flat bar (a-36) cut to 6" squares. Pistol distance from 15 to 50. Also have a 3' circle that is 1.25" thick at the shop for a 1000 yd gong. The options are endless.