I will be installing temporary wiring for an RV which has a NEMA 14-50 plug. The RV does not actually need 240v, it just splits the load between two 120v legs. I want to use a 30A 120V circuit breaker, and put a 14-50 receptacle on the end of a cord. A common way to do this is to use a straight TT-30 cord with a 50A to 30A "dogbone" adapter, but in order to have one less connection, I'd like to wire a 14-50 receptacle directly to the cord, like this one.
My question is, how can I bridge the two hot legs inside this receptacle? Is it safe to use a short jumper wire for this?