Wanye and Free...great points! Free post, some pics pls. Yes sawdust and such is being silly..but water lines with a kink..not good! The point is not just leaks...Sitting on a truck for 80,000 miles its shakes alot and the weak stuff will give out...i.e. the bracing under the slide out is bending and dropping, started to have issue with slide motion if not exactly level without the jacks down...if down sometimes won't even move that is poor engineering and just not good thinking. For decades campers have had issues with the back skirts rotting no matter what...so why not make that section out of something that will not rot or even get water soaked...fiberglass boats for the most part do that...yes there are transome issues with some manufacturers back ages ago...but they changed methids and voila no more rot...it can be done!
Granted anything with a seam is open to issues...designs of heads in RV's is so simple to solve...build a total watewrtight compartment with a drain in bottom, even if it is a dry bath type...if only for ease of cleaning and have a step over at the door...like ships have...any issues in the head stays in the head.
Anyway it just isn't the leak issue it is the whole thought process in design...I bet if thye started thinking about ease of cleaning inside...the so called "lady factor" would take a different slant...why not create a floor pan for a camper with a drain in the corner to wash the floor down the drain...this drain would not need to go to a tank, but could if regulations required it, and the sink tap had a small coil hose attechment and wash out the mud and sand and whatever. dry with towel and clean floor...yes cabinets would need to be waterproof materails..so be it..cost of doing that to all your units would be comparable to wood stuff and far lighter...and the simple design would make the inside appear bigger...benefits all around...aircraft over head bins are a good example...honeycomb covers. But flat material is made already...not a need for molds.
OH well! Just having fun with the thoughts! Have a great day.