While the fully boxed frame rails have to be the main contributor to the "9 times stiffer" frame, is anyone worried about the salt and muck getting in and not out? I usually have not had aftermark rust proteciton applied, but in this case I think it may be a necessity. Just wondering what the consesus was........

 

I think it's a valid concern. I had an old 72 Cadillac that spent most its life in Michigan. I ended up junking it due to severe frame rot behind all 4 wheels.

I would highly recommend spraying an oil-based corrosion inhibitor (i.e. waxoyl) into the frame rails.

 

See below...

 

There is a world of difference in the type of steel used to build this frame and that frame on your old Caddy. The use of zinc, trace bits of aluminum and other chemical wonders make modern vehicles much more corrosion resistant.

Application of an aftermarket coating probably would not do anything and could possible harm the factory design by closing gaps intended to allow moisture to drain, or evaporate.