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Are you leaving your tank on the front rack of your ATV the whole time?
Have you tried the Flameking rechargeable propane system? There is an upfront cost but very convenient to bring a couple of 1 lbers on a trip and recharge as needed.
Mounting the tank on the towbar sounds good to me, like mounting on the tongue of a camper. Though I'm sure the towbar can get bouncy out on the ice. Might want to look for a mounting bracket with a cover. I can see it getting pretty sloppy right behind the wheeler.
Refilling my own bottles spooks me, I don't trust myself or the bottles/relief valves enough not to have a "boom" in the garage in the summer. Won't be using refillable bottles. Call me chicken, but I just won't do it.