I’m the opposite. I get more frequent erections when an extender is part of my routine compared to when I’m just do hanging or manual stretches & no extender. I stretch with a lot of tension too, but usually not more than 1:30 per day. There are a lot of different ways to wrap and make it more comfortable, and most techniques have been posted at some point. I use a dry baby wipe wrapped around the silicone tubing, but it sounds like regardless of wrap it might not work for you.
Mid 2006 ≈5 NBPEL -----> Mar 2011 >7" NBPEL