I have a fused spine and back pain; I normally sleep on a zoned latex mattress from flobeds.
Every year my family spends a week in a tent cabin supplied with cots and saggy old spring mattresses. And every year I am miserable at night. I am desperate to shore this thing up even just a little, but don’t have a lot of extra packing space. Can anyone suggest a way to make a spring mattress a bit more supportive? Would a hiking air mat do the trick?
Hi Lnkholder,
Welcome to the Mattress Forum! 
I’m sorry to hear about your back issues, but you certainly have a mattress using good quality componentry at home.
The first thing I’d look at would be the surface upon which the mattress was placed and see if that would benefit from a firm and flat upgrade. Sometimes these tent cabins use bases that have a quite a bit of sag to them and they can often be reinforced.
If you are considering a new mattress and limited in space to transport it, you may wish to investigate a piece of high density or high resiliency polyfoam of a bit of a firmer ILD, or a piece of latex in a bit of a firmer ILD. I don’t know how thick you’d be able to transport, but a thicker piece in the 5" – 6" range, placed upon a firm surface, with a covering over the foam piece, can be quite comfortable for such trips and can also be rolled up for easy transport. At a quick glance, there are even some members here of the site who offer finished latex mattresses or polyfoam cores in the 7" range, such as SleepEZ, Mattresses.net, My Green Mattress, Rocky Mountain Mattress, Flexus, Sleep on Latex, and Latex Mattress Factory. You could also create your own mattress of a specific thickness using some of the companies listed here in the component post. All of these options would be more comfortable that an air mattress.
Phoenix