i am going to my first 1,000 yard F/TR class competition in a few weeks. My shooting buddy has noticed me fidgeting constantly with my cheap rear bag. Up to now, I have shot only up to 600 yards. He says I better get a good solid rest for 1,000 yards. Any suggestions? I am shooting a Savage 10fcp/Mcmillan .308 which I love. Shooting off a Harris bi-pod up front. I like this set up. It works pretty well for me. I just need a stable rear platform to help me "stabilize" my sight picture. Any suggestion appreciated