Hi @f1partisan160 If the pad is perfectly flat you could make a baseplate replica out of 1/4" plate steel to use as the shim. If it's not flat or you do not have access to the steel or tools to make a plate like that, steel concrete shims can be used. These usually come in a box at the big home centers in the concrete section, next to rebar and grout and tie straps. I believe the box is about 5 lbs and has 1/16 - 1/8" shims that measure about 2x3 inches or so. I don't recall exactly. Hope this helps. Thanks