So hey, after some further investigation and a visit by a friend with some metal working experience... turns out it's a paint problem!

The untreated sheet metal was spray-painted on the interior of the storage compartments. (if it's galvanized at all, it was a minimal treatment, at best.)

The exterior of the bins are brown with rust, but intact... think like a rusty brown railway bridge. The coat of rust protects the steel. With the storage compartments, the problem starts with retained moisture under the interior paint skin.

The bins are rotting from the INSIDE out! It has little or nothing to do with the weather or road conditions.

There seems to be no immediately available or cost-effective means to restore or replace the rotting storage compartments, so I have resorted to patching with sheet metal, gobs of construction adhesive, 1/2" plywood and slotted angles... and a bucket of bolts and tapping screws.

https://www.winnieowners.com/forums/f259/rust-crud-and-corruption-364890.html

AZDEL panel walls and double-pane windows in our Minnie Winnie create a warm (or cool) coach, but the heat loss/gain from the cab is a real challenge, especially during a cold northern winter.

I have zipped two winter sleeping bags together to isolate the bunk and the rest of the coach from the cold of the cab.... window reflectors and a lighter curtain are usually sufficient in the summer. Conversely, if you can reduce heat loss into the cold cab, you don't have to deal with the insane frost and wetting on windshield, cab doors and windows.

The sleeping bags keep out the cold but they aren't really air-tight. There's still a bit of heat and humidity lost to the cab, so I also leave the cab windows open a crack in winter, with a little USB fan running on the dash to move some air through, and reduce condensation.

We were experiencing a lot of noise inside the coach, from the undermount Onan 4000 gas genereator - waaay more noise than outside... what the heck? The tailpipe noise is minimal, even without a muffler and the generator itself is tolerable outside - but inside was a serious racket!

With propane heating and our solar setup, we don't use the generator for much more than the toaster, coffee maker and microwave. Our climate rarely calls for air conditioning and we're not full-timers, so it took me about five years to finally focus on the noise issue.

I can't really explain how I got to the conclusion but when I had my "Eureka" moment what I realized is, with the Onan 4000 being mounted to the frame, we were experienced vibration more than noise from the generator. The hollow plywood bench boxes were acting like loudspeakers, turning the generator vibration into full-throated sound!

I chose a Rockwool product called Comfortboard 80 which is a semi-rigid product, easy to cut and fit. This product absorbs most of the sound and has the added benefit of providing a thermal insulating value of R4.2/in.

I found condensation and ice behind some clothing in the rear bedroom closet, which is on an outside wall. The exterior walls are AZDEL panels, with a specified insulating value of R7 which was not entirely effective at -20C (-4F)

We had lots of heat, but the heat loss through the closet walls and ceiling was a problem, especially with lot of heavy clothing stowed in there, and the closet doors shut. Seems okay now, since I lined the closets with Reflectix. I covered the Reflectix with indoor-outdoor carpet to protect the insulation and give a better look. The Relectix is adhesed with two-sided carpet tape, and the carpet is laid on the insulation with really sticky mounting tape.

I found condensation under the mattress, up at the front of the over-cab bunk, overnight in January - it was about 0F (-18C) at Algonquin Park in eastern Ontario. We had lots of heat, but the isolation of the wall and deck behind the mattress was a problem. Seems okay now, since I lined the floor and lower wall with reflectix. I covered the deck with indoor-outdoor carpet to protect the insulation and give a better look. The edge of the carpet is finished with automotive trim. The Relectix is adhesed with two-sided carpet tape, and the carpet is laid on the insulation with really sticky mounting tape.

Intalled 4x100W Renogy solar panels and 40A charge controller; replaced 2x lead-acid coach batteries with 4x Trojan 24-AGM deep cycle. Closed battery box external vents, insulated stepwell battery box and opened to interior. All batteries operate at room temperature now, even in winter, when the furnace is on. Added a 1000W pure sine inverter and now we're watching TV now without hookups or generator running. Panels are charging coach batteries nicely during daylight hours, even on overcast days. Three thumbs-up for Renogy systems from California.