What a terrible place for it. Mine started to leak at the back flow stop on top, I'd make sure all your clamps are tight to ensure you don't end up with water leaking into that cabinet.
I have the exact same travel trailer. The black tank flush did not work well at all. There was a kink in the tube behind the wall. Also the black back flow device was leaking. I changed it out for a brass one. No leaks now, and the thing works great now.