You might want to wander over to TRVN (TiffinRVNetwork.com) to search on the subject or ask if anyone is willing to tell you what they got.
Realistically, 30 percent is the upper range and that's with a dealer who is willing/eager to work with you.
I don't know anyone who has gotten 35% off a new coach, but I'm sure someone out there will claim they know someone whose brother's neighbor's second-cousin's priest got that deal.
Our local dealership in VA offered a little over 10 to someone we know. (Neither of us purchased there.)