I tow a 28' V-nose featherlite behind my 39' 6" diesel pusher. The trailer is actually 33' from tongue to taillight.
I use something called a Air-Safe hitch. It is an airbag suspension for the trailer that slides into the RV reciever. It also allows me to use the WDH bars. with this setup, the RV and trailer really work well together.
Another thing I did was to have a custom hitch built for the motorhome, as the OE was only rated for 500lbs of tongue weight.
Overall the trailer has a 66 GTO, electric golf cart, kids toys and junk in it, and it usually weighs around 9500-9800lbs. It's a 10,400 rated trailer. Tongue weight scaled in at 1300lbs on my last trip.
I have no porpoising issues with the airbag and WDH bars - without it is not the most comfortable ride...
http://www.airsafehitches.com/receiver_hitches.html#Class5