From what I can see, the main reason to have an extended hitch would be to keep the top of the trailer from hitting the MH while going through a deep dip. As such, I doubt that I could ever get my Class C MH through a dip that was deep enough to cause that issue with my flat front trailer, unless maybe I was also turning tightly at the same time. As for turning, my MH will not turn tight enough (going forward) to require an extended hitch on my trailer (7x16 box, 20.5' overall length) and I would guess that is the case with most, if not all MHs. After all, if standard trailer tongues were designed short enough to create that problem with a MH, then every truck pulling a trailer would also have that problem, since they are likely to have a tighter turning radius. I believe that trailers' standard tongue length should be sufficient for all but the tightest turning tow vehicles, which MHs are not.
Loaded, my trailer is around 4K pounds. No WD hitch needed, barely drops the back of my MH an inch or two max. Tows beautifully; other than uphill I barely even know it's there. Never needed a backup camera either, it's one of the easier trailers to back that I've ever owned becuase it's long and visible in my mirrors.