[Cantrell]

Our A/S is stored under a covered porch which is great for keeping direct sun off it but it does create an environment inside that encourages mold growth--especially here in humid, coastal SC. I keep a regular sized dehumidifier running on medium speed all the time when it is stored (it sits on the kitchen counter and drains the condensate into the sink, grey tank and then out into the yard harmlessly). This helps a great deal--no musty smell, cabinets doors don't stick, etc. This may be a helpful solution to start out your trip with most of the humidity removed from the trailer before you leave home base--the AC won't be struggling to catch up and pull the moisture out during your stay in it. It does take time to get moisture out but once you get there it can be maintained pretty well even if your unit is slightly oversized.
Something else that may not have been specifically mentioned is to run the AC on the lowest fan speed available. This will allow the compressor to run longer during each cooling cycle and allow more moisture to be removed over time. I don't know if your unit has only one fan speed option but there may be some way to adjust the fan speed internally.