How long is too long for camper

Since all truck campers are designed for pickups with a standard 8' or shorter bed and a CA of 56" or less, I think any truck camper you can buy will go on the shorter truck. The longer CA would probably handle better, and give the option of mounting the camper either further forward or further back on the bed. Further forward would give better handling and a porch out back (though many campers assume anything aft of 8' is open and have drop downs, drains, etc there). Further back would give you a big space to use ahead of the camper for storage, a motorcycle, or whatever you can think of. Also the cabover would not hang over the hood as far.

In my opinion the big win for a flatbed camper to to change the floorplan as it is now unrestricted by the pickup box and wheel wells - but that requires a custom build. I considered for a time buying a chassis-cab truck and mounting a small 5th wheel on it, like the old Bigfoot 5th wheel or the similar Escape 5th wheel. That would be a phenomenal setup. They amount to about a 13 or 14' camper but not confined to camper floorplans, with side entry.

HMS Beagle Thanks, yes I am planning on going custom with the camper, I did never think about the possibility of a small 5th wheel like you mentioned. That is interesting. I saw an Oliver travel trailer on a flat bed Fuso that looked pretty cool.

I plan for a spare tire, and a light Honda CT 110 motorcycle on the back.

Ok, whatever you want. Personally I'd pick a camper I liked and then buy an appropriate truck. Difference in handling and ride won't be that much.

The longer campers drop in the back so it's not like you can position the camper anywhere on a flatbed. If you were to get the longer cab to axle wheelbase, the storage would be in front of the camper. I'm having a 9' low profile camper body built on my Ram 5500 and picking it up next week. The 9' body gives me a nice 10" wide storage space up front (think oversized cookie sheets) that's designed to carry the tailgate. I have an acquaintance that has the 11' body with a Host Mammoth. He has a huge front storage cabinet in front of his camper set-up that almost looks like a sleeper. Google Douglass Truck bodies in Bakersfield to see different campers on different makes and wheelbase trucks.

Don't forget about these people for a custom flatbed camper....
Custom camper for flatbed

I'm going to chime in and say length alone will have little bearing on handling.

I, like many others here, have had several TCs over the years. I had an 11.5' Real-Lite on an F250. I've had a 9.5' on that same truck, then moved on to single-slides, and now my dual slide.

I can say without a doubt that height and weight are far bigger factors than length. Length on it's own won't be a factor since most all are designed with a mostly normal COG. Add slides, now it's heavier. Make the inside floor go over bed the rails like mine, vs inside the box like my previous Arctic Fox's, and now you have a taller TC, which tends to sway more.

All but one of my TC's were 11.5'. Weight and height made me go from an F250, to a 350, and now a 450. Length alone was not the factor.

I've been considering exactly what your thinking about: buying a 5500 series truck with a flatbed to haul a large camper. I like the idea of the better ride and balance of using the 84" CA with the 11' bed. Not all of the big campers can be put on that because many of them do drop down in the back beyond the 8' mark. However, many of them don't do this. It seems like a lot of the larger campers that have the floor at the height of the truck bed sides are flat on the bottom all the way to the rear.
My preference would be to find on of those campers that is flat on the bottom and put it on an 84" CA truck. This would also allow for towing with a much shorter (or none at all) hitch extension. The only real downside is that when driving just the truck it would be longer. However, I really wouldn't drive it much without the camper so that's not such a big deal.

Since you are going custom build, the 84" CA would be my choice. Longer wheel base does ride better and will allow you to have the COG in front of the axle for sure.

However, look at the front axle capacity and see if how much it has to spare. Then do some calculations on how far forward you think the COG will be and make sure the front axle can handle the weight. You may find the shorter CA would work better.

I am leaning toward the 84". Like I said the total length and wheelbase is about the same a regular crew cab with 8 foot bed, but instead with a 10.5' or so flat bed.

I am looking at a company called camperlogic.com for the camper, they have a build thread on this expeditionportal website, and it seems like its' pretty well built and insulated.

I can get just under 9' of my 11.5' Host Mammoth on my flat deck. I was able to load 7.5' of my short bed Arctic Fox 811 on the same deck. The camper will sit over the axle the same way whether you choose the 60" or 84" CA option due to the rear overhang that holds the primary fuel tank. A custom flat bed camper throws out all the assumptions because you have more control of what is hanging from the underside. If you want storage between your cab and camper, get the 84" CA model. If you want the shortest vehicle with the tightest turning radius, get the 60" CA model.