Has anyone used Rain-Ex on the nose of their 5th-wheel?

I think Rain-ex is pretty powerful stuff and I would be a little careful.

I've used it many times in the past, using a wash cloth to rub it all over my windshield. I remember that on at least one occasion I picked up my rain-ex wash cloth after it had been sitting on a shelf in my garage for a couple months and it basically crumbled into dust. Kinda weird.

* I have also used Mcquires - it works great.