Just as a data point, I made a harness out of this material from strapworks:
https://www.strapworks.com/Polyester_Webbing_p/pew2(10k).htm
It's a bit too flimsy. It stays in place, triglides don't move around, etc. It rolls up nice and tight for packing and is comfortable in just a rash guard, but the shoulder straps would roll occasionally when I went to put my bp/w on. It's not annoying enough that I'm going to rush out and replace it, but if I were buying again, I'd want something firmer.
https://www.strapworks.com/Polyester_Webbing_p/pew2(10k).htm
It's a bit too flimsy. It stays in place, triglides don't move around, etc. It rolls up nice and tight for packing and is comfortable in just a rash guard, but the shoulder straps would roll occasionally when I went to put my bp/w on. It's not annoying enough that I'm going to rush out and replace it, but if I were buying again, I'd want something firmer.