Do they exist? I remember seeing pics on here of a hi-side/demo trailer built by somebody down south. I thought it was a quarter frame, but i can't seem to find any high side quarter frames. Is there are reason all the hi-sides i can find are frameless besides payload?
are you talking about the clement Monstar's? http://www.clementind.com/Scrap and Demolotion Trailers/scraptrailerbillboard.htm
Quarter frames are mainly built so they can be used to haul asphalt. I am sure the trailer manufacturers would build you a quarter frame demo trailer if you ordered one, but for the most part the quarter frame is viewed as unneeded weight on a already heavy trailer.
Palmer trailer in Mississppi used to build some decent ones. Quarter frames are good for asphalt, dirt, muck, etc. and good for stability. Look in the Chicago area if you're looking for a short 22' - 26' type trailer.