Do the test hang first.
I found the same issues as Beast 71. I had calf pressure from too taut a hang (got to check that ridgeline as Brandon shows in his set up video - make it as loose or looser).
I had my UQ slip off my shoulder several times. I made a couple of grossgrain loops on the sides. Get a mini biner or dutchhook to hold the Incubator's side loops to the ones that you sew onto the WBBBs.
Another mod was to get a couple of glow-in-the-dark zipper pulls.