Dear Little Scrapper,
Holy parts-count Batman!
You could do the same job with a simple loop of webbing. You can pre-sew the webbing and slip it over the cabane struts before you bolt on the top wing. The horizontal strap only needs to prevent shoulder straps from slipping below your shoulders. Who cares about upward loads?Parts-count = 1.
I still recommend routing a steel cable back to anchor near the tail wheel. That way-back anchor point provides a better angle to reduce vertical loads on your spine.
But that is just the opinion of an old parachute rigger ... and even older helicopter mechanic. Yes, I know how to use a torque wrench, but am much quicker on a sewing machine.
Also, a crotch strap (fifth point) will keep the waist-belt in place and reduce the risk of you falling upwards (negative Gs, roll-over, etc.).