Ok, here's my plan. I gave up on finding the special sling but I have a better idea.
Sit down in a crossed leg position. Take a strap or loop of rope and wrap it around your legs just below your knees and up under arms and around your back. (simpler than it sounds)
Take your spotting scope tripod, scope removed, and set the legs low enough so the tripod head reaches just under your right armpit. Place your sand sock on top of the tripod head. Now lean your weight against the tripod head slightly. Using a Harris bipod, place the toe of the stock on the leading edge of the tripod-supported sand sock. Use plenty of back-pressure on the stock.
This was my first group trying the method at 700 yards in a variable wind. I don't try to adjust for the wind after the first shot when evaluating loads or shooting positions...thus the wide horizontal spread. The top shot I called high. The other 9 shots went into 5 inches of vertical. I'll take that kind of sitting position accuracy any day...but I think I can do better with some practise of my new system.
[ 07-26-2004: Message edited by: Len Backus ]