This is the danger of having too much capacity. I know with ours that the humidity in the trailer starts to rise at night so my thermostat setting doesn't provide the comfort that it does in the day. I usually have to go down a couple of degrees to get a little more run time.
I'm going to assume that you allow the fan to cycle on and off rather than allow it to run continuously. Constant running of the fan will allow the humidity to build up even faster in some cases since the water left on the coils will evaporate back into the trailer make it all the more clammy.
Variable speed compressors that are found in homes usually require DC fan motors that have speeds that vary dependent upon compressor speed, which are very expensive. At this point I'm not sure of the market is there to justify this kind of technology in RV units. In a home unit the major use of these types of ac units is energy savings.
'04 Classic 30' S.O.,'03 GMC Savana 2500,'14 Honda CTX 700