Mark, As long as the wire size is appropriate for 30 amps, the plug really doesn't matter since you have a 30 amp breaker feeding it. Now if some one were to put in a 50 amp breaker and only have 8 or 10 gauge wires, then actually draw 50 amps, the wires then become the fuse as they are the weakest link. As it is now, if the wires are the correct size for 30 amps, the most that can be drawn is 30 amps, then the breaker should throw. So the plug size being greater than 30 amps is no issue.
To a small child, the perfect granddad is unafraid of big dogs and fierce storms but absolutely terrified of the word “boo.” – Robert Brault