Originally Posted by markdoane
I can't think of a reason why you couldn't run two 30amp plugs on a 50 amp 3W+G cable.
I thought of a possible problem. If both the 30a receptacles are the same phase, you could possibly have more than 50amps coming back through the neutral.
Best to build a cheater box, and put a 50amp breaker on the neutral. You will need to use full size 50 amp, 3 wire cord with a separate ground. One of the 30a plugs goes to the black leg, the other to the red leg, and both the 30a neutrals connect to the white, which is protected by the 50a breaker.