I am having a 17 pound BAT DS 6BRA rifle built and will be using a Shehane Laminate ST-1000 stock. I don't have access to a stock to measure so can someone please tell me which rear bag works best with this stock? I currently have a Tooley MBR on another BAT but it has a very narrow butt width and I use a rear bag 3/8" spacing between ears. I recall buying 4 to 5 bags to get a good fit on a Scoville stock some years back and would like to not repeat that cycle again. Thanks in advance for your help.