I've used a Neilpryde Seat harness, not the full on race one, the one with a bit more back padding and haven't had any problems so far. The color has faded a bit but I try it in the sun and don't always rinse it with fresh water.
I love seat harnesses. At my weight it's super easy to get overpowered and, with your lines in the right place, you can just put all your weight on the rig, which makes it super easy to get in the back strap and blast.
I don't think you'll regret changing.
JP Super-X 106l, North F8 Ram: 5.8m,