Just to run the electrics in the Globetrotter I have to use 50 ft of cord to reach the outlet in the garage. I'll run the A/C or electric heater, then power up vacuums, saws, drills, lights, whatever while working inside. Never had a problem.
If you think there is a problem get a multi meter and check the voltage under load at the outlet and in the coach. While I'm not certain, any thing over a 8 volt drop would seem excessive. Most of my drop came from the aluminum wiring oxidizing at the outlets.
If you need heavy duty cord I have seen 6/3 50 amp neopreen covered line at Home Depot. Think this will handle just about anything.
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