The photo was taken sitting on the HH. Standing up puts the chest roller almost to the HH. With the HH clipped directly to my harness (rock climbing type), if I attempt sit back onto it, the roller pushes the hitch down.
Yesterday I used the HH clipped to the harness normally and the chest roller, but added a hand ascender above the roller as my connection point while climbing. I took the rope off the chest roller and removed the hand ascender once I was up where I wanted to be. This worked well and I could use the hand ascender to set up a 3-1 for short moves when needed. I also took my first baby steps away from the trunk out onto the limbs.
As for webbing tethers, I have no problem sewing up anything I need.