I have the answer!
I tried every suggestion on this forum, and the only one that worked for us is putting HyperVent Marine under the mattresses. It's a bit spendy, but our first outing was 4 weeks at Camp Pendleton, and wiping down 3 mattresses and bunks and setting a fan every morning was NOT going to be an option for me. Go to HyperVent Marine - Putting An End To Condensation
and check it out. I could even send you a small piece of my leftover, if you need to see/feel it before you order. Call 360-657-5503, and talk to Rex. He's great, and will walk you through the process. I was so frustrated with the wet bunks, I told him if this worked, I'd advertise for him forever. And I will!