I own a Key Largo as well and for the first 4 months I towed it with my '07 F350 SRW 4X4. Not long after I went and bought an '11 F350 DRW 4X4 and it was literally like night and day while traveling down the road. I have no doubt that physically a 250 could tow it but I can say I would definitely not want to do it more than I absolutely had to. Technically it is too much trailer for the truck but almost everyone knows someone that "has been doing it for years with no problems". Even in the SRW 350 it always felt more like the trailer was more in control.
I have airbags, programmer, etc, etc, etc on the '07 and the dually is completely stock. I know I will not go back to towing a heavy 5'er with a SRW again. No reason to.