SRW vs Dually

Here's a bit of a twist if you will on this topic. On another forum, a poster states how he is getting a toy-hauler w/a dry GVW of 16K and max GVW of 20K. Has a '03 F350 SRW w/ 7.3 with things being modded. Most of the replies are telling him he should be looking at a dually, but he insists the '03 will do just fine and is even considering making it into a DRW (states the frame is same for SRW/DRW for year). Ford says max 5er wt is 12,700 for that year. Don't know about ya all, I'm heading' in opposite direction.