I've sen 3" mentioned before. I've also seen some comments that some Fords had more frame flex than other trucks. My current truck (2000 K3500 crew cab long bed) has 2 1/8" between the center of the cab and the bottom of the camper overhang and hasn't hit in 20 years. But I only use a 1/4" thick rubber mat in the bed which minimizes the amount of camper bounce.
Truck manufacturers brag about how strong their frames are on new trucks, I just wonder if that translates into less flex between the bed and cab. I'd prefer to keep my center of gravity as low as possible and minimize the amount I have to raise the camper.
I have about 4, i could get away with and feel comfterable with 3.
frame flex doesn't mean it is weak, a fram that will flex in most cases will usaly be stronger to a point as it is able to adsorbe slight movment where as a ridgid fram can't and will be work stressed and eventual fail. now we will probably never see thins in our picks ups but just wanted to put that out there.
the major issue you are going to see is if the brand crowns the bed for weight handling, this will let the camper rock back and forth more which lets the cabover get closer and farther away from the cab roof when hitting bumps and even accelerating and braking. some people have made up for this by shimming a bed suport up to make a flat surface for the camper to sit on but then your defeating the purpose of the crown, so I am not sure what the answer is in this case, maybe some one with a crowned truck can chime in on this one, but it is a good idea to get a knowen strait edge the length of you bod and see if the bed is crowned or not then you know.
As far as I know the crowned bed is limited to GM trucks but I'll verify the Ram bed isn't crowned with a straight edge.
