I have a former dump truck (Western star) with 15 feet of frame over tandem axles. What are your thoughts on converting a heavy duty 24 foot flatbed into a forestry/dovetail bed to haul a DGH. Though about leaving 16 feet flat and cutting the rest off to create a 4-6 foot dovetail.
http://images.craigslist.org/00x0x_j4h41BLpOpK_600x450.jpg
I don't know why it wouldn't work. Maybe put some legs on the ramps for support when loading. I've seen dozer beds for a while but have never been around them, just lowboys and tiltbeds.