Not sure if this has been mentioned here before so I figured I'd share. I saw this tool on Amazon while wondering around the web looking for new ideas. It's a 4'' Lab Jack which I've paired with a super sturdy mini-tripod. This combo, I am very pleased to report, gets the job done just perfect. The 4'' plate (comes in various sizes) is a prefect size for any standard rest bag (Allen in my case) Max height on this blue model is 7'' which was fine for me (the bag adds additional 4'') weighs 14 OZ and will hold up to 22lbs. The knob allows you to fine-adjust your hold over/under super fast and easy. IMHO much better than pulling/pushing/adjusting a rear bag for the right spot.
excellent execution.