HDT Toter use?
 

I was browsing Truckpaper and looked through the HDT "Toter" section. These are the HDT's set up for hauling mobile homes. They have a shorter wheelbase than regular HDT's but appear to be the same in all other ways.
How come no one uses these to convert to 5ver haulers? Are they geared different than an OTR HDT?

I'd guess maybe because most of the guys pulling 5vers want a big deck to put a car or golf cart or motorcycles or a big storage box on? And most want a sleeper cab, are these trucks you speak of day cabs? Just my guess.

that short wheel base would ride real rough.

Those mobile home "toters" are a very short wheel base, and set up for a bumper pull type hitch and typically are not long enough to mount a fifth wheel. Definitely not cost effective to lengthen the frame, there are way too many cheap tractors on the market to fool around with trying to convert something purpose built like that. Far cheaper to single up a tandem and cut the frame if needed.