I spent a while trying things, puzzling how to resolve the issue illustrated in several YouTube videos: A trailer tailgate isn't suitable for the unloder same as a pickup's tailgate. This unloader can only replace the tailgate, it can't be mounted with the trailer's tailgate in place.
Bringing home gravel with no tailgate would be a traffic safety issue and would likely cost me a ticket.
The best (only) solution I've come up with is - a temporary mount for the unloader that installs with the same downward pins as the tailgate. These pins go down into the rear crossmember.
Then to use the unloader - before loading gravel on top of the fabric, unspool the excess fabric out the back onto the ground, set the tailgate in place, then loop this excess fabric and its axle up over the tailgate and carry it on top of the gravel on the way home.
At home, lift the taigate out and set the axle with spooled excess fabric where the tailgate was.
This would need a mount with two big pins facing down, same as how the tailgate attaches now. Fabricating that 'artificial tailgate' mount should be simple. It would be similar to the trailer adapters others have in their YouTube videos, except removable.
Anybody have other alternatives?