I shim the rear recoil lug and at the front of the crossbolt, if you make the shim at the crossbolt tall enough to grab with needle nose pliers you can shim it really tightly in the stock and be able to remove the shim to take the rifle out of the stock. If you only shim the rear lug it’s so tight in the stock that it can’t pivot out, I generally use feeler gauge stock or spring steel shim stock.