What are the possiblities of installing a wye (inside the boat), a couple of full-open valves and a through-hull fitting appropriate to the RV site? Just a thought.
I had considered putting a "Y" valve on the galley and shunting the gray water to 5 gallon cans. This is the way I rigged a Van to mini RV conversion I did--worked fine.
Several years ago I stayed at a campground in Utah and couldn't figure out why when all the neighboring campsites had great TV reception, but all I got was crappy reception..... :roll: