Wish we had more room to work with, but I'm limited to the 14ft box (3ft attic) - I needed 8ft in 7'8" in back to fit dirt bikes or the 4x4 ATV
I did look at the larger 24ft trucks, but I thought the length would be a negative maneuvering around city streets getting to the race sites, the height overall and step height getting in and out, plus the extra money to operate kept me in the smaller truck.
As far as room.. I raced the past few years out of a Ford E250 Extended cargo van, so this should feel like a mansion.