IMO, the 'tow rating' does not mean a whole bunch... Take my rig for example..
The towing guide says #11,300 for my trucks specs.
I'm towing a #7000 GVWR TT that's loaded up to the gills (on purpose) and I load the heck out of the bed of the truck too (on purpose)..
The truck tows it well, and that's what I was going for.. I don't want to tow something at it's max.. The towing experience would be terrible (for me anyway) and that's not why I 'camp' in the first place..
Anyway, pay attention to the trucks GVWR and it's payload.. The higher the numbers, the better.
You have to 'decode' the axle code, but in my case, that's 3.73..
I know I'm maxed out on my trucks GVWR and payload when I'm all loaded up.. But, that's fine as it's still a comfortable tow. I'm just no where near that magical 'tow rating'..
So, choose 'wisely' for both the Mule and the Cart when that time comes. :)
Good luck! Mitch