Many snow-kiters have combined a climbing harness with waist harness in the past to back-up for safety when doing small glides in snow. The crunch factor is hard to control with these leg loops. Also too much uneven/unpredictable transfer of power from hook to femur. There's a long way to go in this area.

The ideal connection point would be joining the legs to the waist harness via the spine area, emulating (or not interfering with) the natural twist of torso. The leg part would be fitted and lower, well below potential marital harm (not crushing the family jewels please). The tricky part is how to make it not look funny. Don't tell me I gotta wear boardshorts over it. Tall order I know.

Ideally it might have to be an integral part of the wetsuit, with an attachment point for the harness at the base of the spine or across the hip joints.

Or.... Just go and get a another seat harness and have two? Just an idea...

"Or.... Just go and get a another seat harness and have two? Just an idea..."

Well, yeah, maybe so. The OP is possibly trying to save a buck and I am saying the ideal harness does not exist yet. I keep buying harnesses that fall far short. When I quit drinking I will invent the ultimate harness. In the meantime heed my sage advice. Hiccup....

Lol

THE MOST ADVANCED HARNESS IS COMING...
You could try to improve our design

I was thinking about this last weekend lookking at memory foam bras with the wife. Something with a small cup size and a 31 waist.

Pics of the mod to my mystic shadow harness mentioned above (sorry for the late reply).