Gimli, I bought a set of sliders from RSG in the summer of '18 without any knowledge of their weird "trimming" warning.

After mounting the right slider, to my surprise, the rear door could not be opened more than a few inches. The interference had nothing to do with the plastic cladding on the door. The slider was angled too high for the door itself. I would have had to "trim away" a large chunk of the steel door, leaving a hole about the size of a pack of smokes in the door!

I exchanged the sliders for a set they built flat with no angle whatsoever. Although the replacement sliders stick out quite a bit more than I wanted, they've worked out great and protected my truck from several boulders and stumps last summer.

The steel is thick and the whole slider feels beefy. When installing the set, I got the sense that it was quite a bit heavier than what was listed on their website, which is good, as far as I'm concerned.

The only downside to a flat RSG slider is that my leg always rubs it when exiting the truck. There's always a clean spot on the slider under the driver's door. If you can live with that, ask them to build you a flat set.