That width should be at the wheels/tires. The floorboard area is only slightly narrower. Unfortunately, I no longer have my '06 XP or I'd take some measurements. But I can tell you from experience, they will fit on a 5' wide trailer unless somebody has installed aftermarket wheels (or spacers) to change the width.
thanks commander,
you are correct and the proof is in the puddin'.
just unloaded my new '99 in the dark off of the tilt-bed 5'x10' trailer, forded the creek through about 8 to 10 inches of water and drove, more like riding on a cloud, up to the house.
paul, as in bunyon, told me he likes his new open space in the 4-vehicle carport. he said the floor being on a hillside slope was much more comforting to him, too. paul has a nicely engineered diy removable auto glass windshield, additional high-mounted, forward-facing and on-with-the-key led running lights, new tires, a full-height headache rack, a snow plow blade, hard top, roll-up back sheeting, soft doors and misc. oils, filters and belts. oh, and a package of deer steaks dated nov. 2014 and a package of venison snack sticks. paul has been well taken care during his 358 hours. the wheels had about 2" to spare on each side. sweet, sweet and sweeter. and the rig cost me well under $5k.
have been glad to have the opportunity to chat about newbie and other stuff here with you during the treasure hunt. now, on to researching a double axle open box trailer with tires not unlike those paul has. maybe northern tools, ??
all the best to you for the holiday,
crossing_patoka