I recently injured my left shoulder.While that's been healing and I'm waiting on a Sub 8lb jazz-like bass to arrive I've been thinking a lot about straps.
A long time ago I purchased a strap that I'm going to try again or possibly use as a base to have something made.
It has two things that make it unique. One is a pivoting junction right at the end that attaches to the upper horn. The way the angle the strap is forced to make a to twist 90 degrees is now gone. The higher you wear the bass the less strap distance the strap has to make this twist causing more consequence to it. That twist creates a imbalance in strap pressure on the shoulder. More so on the side towards the arm,away from the neck.(Is this where your struggling Bluesycat?) If your healthy and strong it's possible that distributing the pressure away form the neck is a good thing? I also have noticed that my old school "comfort strap" leather parts are very supple. So if that part is long on your strap it will minimize the advantage of this juncture thing. The other difference is that the whole piece of leather is cut with a curve at the end accommodating the natural curve that the strap wants to take.
The strap as is is too short for me. But I like the ideas.