Sorry to rain on anyone's parade but adding anything more than a scooter {read not a motorcycle} to the rear bumper is simply a disaster waiting to happen. The longer the overhang on a C the sooner it will happen. Most C's are limited to 5,000# of towing capacity and the hitch weights are even more restrictive. Even if you have a newer E450 rated to tow 7500# check your hitch weights carefully
Unless you beef up that hitch with some serious reinforcement/welding done my a very skilled tech you are going to be in for trouble. Think also of the weight redistribution placing 4 or 500# on the rear end. You will in all probability be overloading your rear axle and I guarantee you will be lightening up the front end a bunch {and not in a good way}.
The rear bumpers of a class C are truly it's weakest link and loading it up is never a good idea. If you want to bring a bike {read serious motorcycle...and I do} then do it right and invest in the proper trailer for your particular bike and coach.
I have had three trailers over the last 6 years and have towed everything from my BMW R80 RT in a homemade trailer {not ideal}, to my Harley Dyna Super Glide on a nice Kendon folding trailer with great results.
When I moved up to the Indian Springfield at 875# I outgrew the Kendon, sold it for what I paid and moved up to the ultimate trailer...
A 10' X 6' cargo trailer that is simply my new portable garage going everywhere I go and it not only keeps my Indian out of the weather, road debris and the prying eyes of bad guys it does double duty hauling Rzr when I am so inclined. Either way it tows like the proverbial dream and provides abundant additional storage. Fully loaded the bike and trailer weigh 2,220# the Rzr and trailer come in at 2,600#. I get about 9 mpg towing either way.
I cringe when I see generators and multi bicycle racks {much less a mid sized or larger motorcycle} on the rear bumpers of coaches and never follow them closely as they are all just a pothole away from a disaster that they will share with anyone close behind. :S
As always... opinions and YMMV.
This shot was taken last week at Rice Ranch in Quartzsite, for this trip the Polaris Rzr 570 was inside our next trip it will house the Indian:
:C