We've got 2 cheapies...one from ACE hardware. Has flat top which makes great "coffee" table of sorts. Coffee cup, odds and ends, etc. Just because you have dehumidifier doesn't mean entire RV is getting the benefit. To check and if dehum has gauge see if its accurate with your local airport, that probably has weather station. Get a tiny small gauge and put it in different spots to get a feel for how your rv is drying. Open up drawers, closets ect so dry air get everywhere it can. Wood and mold protection best at 50 55 percent. I have something like this to place around rv to make sure rv is good in places that tend to build up moisture. Very small, got it at Cigar store, they use them to put in cigar boxes. About size of silver dollar, fits anywhere. Calibrate by using local airport for bench mark.
https://www.amazon.com/Medium-Analog-Hygrometer-Humidity-Humidor/dp/B001CZF2DCIf you take it down to low and over a period of time...sucks moisture out of wood trim, wood pic frames, furniture and some people get nose bleeds and headaches from to low of humidity is not uncommon. Especially going in and out from high humidity to low, real frequent and quick. Most airlines fly between 50 and 60 or atleast used to. Not sure today. Don't be surprised how much water you get out of it till you get it "dry". Bt the water you collect is some of the best water for batteries. Made from condensation right off the coils in dehum...before it dropped down into the bucket. I close everything up I can because most Rv's are not that air tight anyways. Where my outdoor shower (thin piece of plastic) is always couple degrees off from gauge on machine. Being you're going to cover RV don't make so air tight you end up "plastic bag" effect". Some air circulation is good, but it does need some.
We had 2 camp spots close to us (foot hills of Cascades) that get a lots of humidity. I used to leave RV during the week for home and work and sometimes only checked on once a month. On our smaller much more portable unit, a good place for it was right in the sink. (Hard to vibrate out and fall) But raised enough so drain was above counter top level, I ran hose from drain to inside a top drawer then up and over the back of drawer then down to outdoor shower. Drilled a hole for other end of hose, made perfect drain for dehumid... Worked great except drops of water sure made the grass/weeds grow more than I wanted.
Don't overlook filters...The machine from ACE hardware has a weird size filter and manufacture wanted lots $$$. If OEM wants to much for filter pick one up at at Home depot (furnace type) and cut them down. Dehum...also cuts down a lot on dust. If you decide against dehum...and get those dry z air things.. be forwarned... look at the chemical they use and think what would happen if you spilled a tiny bucket on carpet empting them.
Currently 70 humidity at SeaTac airport.
OR plan "B"...get one plug it in and it will probably do everything you wish.
