I've loaded many a car with a come-along. A bit annoying but not too tough. Just be sure you have some GOOD wheel chocks as you'll need to pull it as far as possible then chock, pull out the cable and reset, then repeat. Nice to have a helper but I have done it on my own.

The last time I did this I made up some wooden chocks and they worked great - remember that they have to clear the body while it's on an angle so they can't be super huge.

My trailer is considerably higher than a U-Haul and I was able to do it so it should be easier with a lower deck height. Good luck!

Dan