All the doo-dads on a rebreather make things...
sometimes jumbly. I typically have my butt ring open as I place a scooter on there. I don't like a large reel on there because I find it distracting when it sometimes rocks back and forth. Occasionally I've stuck a smaller reel on the ring, but as you described reaching around larger cylinders makes it a tad tough. Depending on the job/dive - our team usually caches gas along the way making reel access easier. I have to say there nothing as pleasing as dumping bulky cylinders along the route.
These days I take multiple Delrin spools (with wider center openings vs. normal) and stick them in my bellows pocket to which I've attached a small piece of rope to the D ring inside the bellows. I just yank em' out out of the pocket and I can see them hanging from the corner of my left eye. The plastic spools don't affect my buoyancy. My buddies also carry the same complement of line so we're pretty good when we need to cover new territory. Since you're cave training I am sure the instructor is developing redundant skills in all areas so it's never easy, or very pretty at the onset as you do & undo lines constantly. Adaptation does take time. And yes - those divers with long arms like a Spider, or Gibbon monkey have distinct advantages.
I curse them all the time underwater as they easily reach valves, and other bits like it was nuthin.' :amazed: