Welcome to JOF
I assume you have confirmed there isn't any moisture intrusion taking place from outside the TT, and/or behind the pass-through storage docking station.
Although I've personally haven't had a condensation issue under my TT mattresses, but as a precaution I did install a product called "HyperVent" under my new mattress earlier this year. The product does keep the mattress off the entire plywood platform and also provides air flow between the entire wood surface and mattress material.
Original "HyperVent":
https://www.hyperventonline.com
Post #225 here:
https://www.jaycoowners.com/forums/f...-51005-13.html
Four years ago I installed (stapled) some "Reflectix" double reflective insulation
under the bed plywood platform and also inside my TT's pass-thru storage to reduce the cold air contact with the wood.
"Reflectix":
https://www.homedepot.com/p/Reflecti...4025/100020855
Post #26 here:
https://www.jaycoowners.com/forums/f...-51005-12.html
Under high humidity conditions I also use a "Ivation" 13-pint dehumidifier with great results in my 24RBS.
https://www.amazon.com/Ivation-13-Pi.../dp/B07B8SCPZ4
Hope this helps.
Bob
__________________
2016 GM 2500HD 6.0L/4.10
2018 Jay Flight 24RBS
2002 GM 2500HD 6.0L/4:10 (retired)
2005 Jayco Eagle 278FBS (retired)
1999 Jayco Eagle 246FB (retired)
Reese HP Dual Cam (Strait-Line)