I just purchased an 8.5 X 20' V-nose Haul-Mark with a 10,400 GVW.
The dealer strongly advised me to get the 18" tongue extension(which I did)because he said that driving over a dip in the road or into a driveway, the V could possible hit the back of the motorhome if I had the standard(short)tongue. It was only a $150 extra, so I don't think he was BS-ing me.
I also like the extended tongue in case I want to put a diamond plate tool box in front of the V and not take up room in the trailer.
My understanding is that a WDH is not needed because tongue weight is determined by properly loading the trailer. Also, I just bought a 2000 lb tongue scale since I want to be sure my tongue weight is about 1000 lbs.