You have a lot of answers, but here is one more: I have a Lamar 6X10 with custom made front chocks and E-Track (loop around the rear tire) for anchoring the rear tire. I did over 3K miles to/from South Dakota from Tucson. Didn't move a fraction of an inch and didn't have to tighten anything even once. Heavy duty with 15" tires and spare. High quality unit.

I wish I had realized the Aluma 638 would work as I would have seriously looked at it.

Rob