I've seen bassists, particularly those sitting down, struggle with their basses walking away from them. Some use commercial endpin rests, some use pieces of carpet, but they seem to struggle with this. I solved it for me with a small, stainless steel cappuccino cup, which has very low sides compared to a regular coffee mug. I sewed some 1/2-inch webbing around the cup handle, and the rest of the webbing loops around a ring installed on a rung in a particular folding chair that is dedicated for playing my strange bass. (You could also just loop the webbing around a stool leg, if that works for you.) With my endpin seated in that cappuccino cup, it's not going anywhere. Totally secure. There's no reason that a double bassist couldn't do he same thing. Just an idea.