The flat bed is an all aluminum custom bed with diamond plate boxes on both sides and does set about 18 inches higher. The tires are 19.5 14 ply so the side walls should be heavy enough. The truck does wander with out the camper on it and it is wander not sway, I do get a certain amount of sway but not bad. I thought it may be because the 450 has front leaf springs and a straight axle. any more thoughts appreciated. It isn't so bad that it scares me but I am used to driving a 3500 CC dually GMC and pulling a 40 foot fifth wheel and no wander what so ever. This is my first TC so it may be normal for them. I do enjoy the TC we spent 5 months in it this past summer so it is here to stay.