I've seen a number of trailers up there. 19' sounds pretty good. I think I've seen a recommendation for nothing over 23' and yet I saw a couple of trailers longer than that up there. Just don't have too low of clearance. Bumper pulls seem fine and fifth wheels appear to thrive. It's not real far from grand Junction so spending a half or full day driving up to scope out the area can be fun and informative.
The road up has some pretty tight switch-backs, and the single camping spots require fording a small stream. Depending on the towing vehicle, and your ability to traverse tight corners, it might be doable. The drive up is not too bad, though. Maybe take a single vehicle first to see if the trailer can make it? I loved the spot, but I took the road up in a Forester.
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