We had condensation issues in cold weather which led to mildew growing under the mattress. Yuck! I added a layer of
DuraGrid marine deck tiles under the (new) mattress 5 years ago and haven't had any issues since. There are other similar products available, such as
Dri-Dek.
Some benefits of DuraGrid is that is is only ½" thick, it is non-compressible, and it only cost $80 to cover the entire cabover bunk area.
I've had the opportunity to check out the Froli System several times and agree that it can be used to make a very comfortable RV bed...
If you are in need of a new bed and your prefer the feel of a traditional mattress & box-spring, it may be a good solution for you. In our case, DW and I prefer a platform bed with a memory foam mattress, and our TC bed is a (very) firm foam mattress with a memory-foam topper.
Cheers,
-Mark