Is it possible to use a 5.5ft camper on 6.5ft bed?

Once that space is filled with other items, some people don't even notice unless it is pointed out to them.

I'm sure it is safe enough although it would be a little unusual looking. It would be better to have the extra fuel lower and under the bed, and tanks are available for that. You can mount batteries either in the corners of the bed or on the frame as well. You could also add solar or a generator to use less batteries.

It is true that with respect to the rear tire the weight will be in the same place, but the relative distance to the front wheels would be 1 ft further back which would impact handling.

I'm curious though ... what is special about the 5 1/2 camper you are looking at?

Kayteg1's example isn't quite the same since he moved the end of the camper is further back compared to the rear wheel. It's got its own set of potential issues. He doesn't have a 9 ft bed in other words.

In my case the space originated from the fact that my cabover was resting on roof lights and I like the idea of extra storage.
My truck is originally long wheelbase cab & chassis so weight distribution is not a problem.
In your case whole camper will fit on the bed, but still the front gap will be the same and with 5' camper I don't think you will have overload issues.

A number of people have upgraded their trucks to long beds, but had short bed campers (like me). You can block the forward section to carry extra supplies, generators or even spare tires. The CG of the camper remains the same over the rear axle, so that extra space is not a problem.

So if I read this right, I think you are saying it is possible to let the shorter camper sit with 1ft room at the front area of the bed, as long as the frame is properly designed to secure the camper... Correct?

I don't understand your "end" comment - would it not fit gracefully at the rear part of the truck since I am offsetting the shorter camper by the right amount?

I keep the 1 foot space in front of my big camper for storage. I made a platform with 3/8" plywood under, than 4x4 blocking against the front of the bed and 2x4 where the camper touches. Small planks on the sides with taper make easy and bulletproof loading.
Camper is hold by "Fastguns" and 1 foot tilt up front is not a problem. That is where spring loaded ties go.
In the rear I found good mounting spot wrapping short chains around bumper inner brackets.
Sounds like your camper will end even with the bed end?
I have no idea how those are mounted.