That's than number I was looking for... 20%.  I've been working on a wing harness but only have memories of seat and waist harness' from when I kited from 2003-16.  I can add a hot tip:  Cynthia Brown has tried a number of loops and concluded 'the softer - the better'.  She has talked of the loop slapping her face like a Deacon's cane. But, she wings at a different level than most mortals.

Jim