A 50 amp adapter will work quite well. I routinely use my adapter whenever 50 amp plugs are available. For the time being, since the 50 amp plugs are "newer" installations and used less frequently, the plugs and wiring tend to be in better condition and make better contact. This will prevent voltage loss from loose/sloppy connections at "well worn" 30 amp connectors. A worn or loose 30 amp connector will tend to drop volt/amp capacity through heat loss in a worn connection (think of the current used in a radiant heater - same principle). You'll be fine with a 50 amp connection, they aren't 220 volt, merely two legs (as opposed to one) of 120 volt electricity.