Just a thought... not all brake controllers need to be kept level. Mine can be in any position whatsoever. I just stick it between the center console and the passenger seat in my Highlander, sticking straight up. I had the shop hook it up with a plug so it can be removed and stuck in the glovebox when not needed.
If it's not that type that has to be level, as long as it's easy to reach in case you need to manually activate it or adjust it, it can be anywhere.
To every thing there is a season, and a time to every purpose under the heaven... --Ecclesiastes 3