I guess I'm the odd one. I have a short (7 or 8"?) level that I put on the frame close to the coupler and use that.
I know it's not perfect, but the interior seems pretty level when I use it, fridge door works fine, oil in a pan on the stove is reasonably centered, and not rolling out of bed, so I guess it's good enough.
I have been thinking of putting a big screw-on level to the front of the trailer, but I can't bring myself to drill holes in the end cap...
2012 RAM 2500 Megacab Laramie Diesel
2016 Jayco Eagle 284BHBE
ProPride 3P WDH