Success! The Loadhandler lived up to it's billing.
Here it is once I got the gravel slid back down and got it hooked up:
And here it is unloaded. It took about 5 minutes to unload. I couldn't turn the handle a complete turn and when I would try to switch the handle it would slip back so I used a pipe wrench to hold it while I swapped the handle in and out.
After it was unloaded I used the tractor to pick up the front of the trailer and even with the plastic it didn't slide out.
I ended up climbing in the trailer and pulled out the plastic and that pulled 90% of the gravel out. The plastic made things much cleaner and easier. I think the plastic was $8. I could probably use it for another load or two if I wanted to keep it around.
Here it is once I got the gravel slid back down and got it hooked up:

And here it is unloaded. It took about 5 minutes to unload. I couldn't turn the handle a complete turn and when I would try to switch the handle it would slip back so I used a pipe wrench to hold it while I swapped the handle in and out.

After it was unloaded I used the tractor to pick up the front of the trailer and even with the plastic it didn't slide out.

I ended up climbing in the trailer and pulled out the plastic and that pulled 90% of the gravel out. The plastic made things much cleaner and easier. I think the plastic was $8. I could probably use it for another load or two if I wanted to keep it around.