I have found a solution for door water leak when towing in the rain for my 2013 LittleGuy
with door manufacturer stamped Challenger Elixir Black 36x26; 0805.
After experimenting with dusting baby powder on the inside of the doors and towing in the rain,
it revealed the water leak was coming from the area at bottom of the sliding glass. My doors had
plastic channel window guides along either side of the sliding glass and nothing on the bottom
Those plastic guides do not appear to offer any weather seal leaving the bottom of the glass
to just sit the empty door frame channel allowed road spray water to seep in.
I replaced those plastic guides with below automotive rubber glass run channel. I ran it all along the
sides and bottom. This sealed all edges of the glass when closed. Now the glass sits tighter in the frame
but still slides up and down easily and has so far prevented further leaks when towing in the rain.
https://www.amazon.com/gp/product/B000M ... UTF8&psc=1Hope this helps