I bought some Talley scope rings for my sons rifle and scope. I purchased the medium rings for the 50mm objective lens but they are too short by the thickness of a piece of paper. Have any of you tried shimming the bases to gain a little height? I know I can return them from where I bought them, but it is a hassle with an online purchase. I was thinking I could cut a aluminum can to the proper deminsions and it would be about the perfect height. What do you guys think?