when we drove out to Moab from Tulsa, OK, a club member flat towed his SIII lightweight. he had installed fwh in the rear and used a D1. it wiggled a lot on the highway, yet, it made it without any problems. as I'm not really a towing person, not sure how to properly set-up the towing procedure so it tows without the wiggles.
if you're going to do this fairly often, get a trailer. much easier all around for you and the Rover.
Jaime