Does anyone know the dimensions for a magazine block for sks? I want to make it 5 rd legal for hunting. My bud can cut me a chunk of aluminum to throw in there. Another guy made one for me for my M1A and he said to drill and tap a set screw to hold it in place on 20 rd mag, Is this for legality issues (Michigan)? I really don't want to poke holes in the sks mag, seems to be fairly easy to just pop it open and drop it in there. TIA