Best advice: Bury a thermal sensor in the coil and see how hot it gets.
I have used a 12 ga 100' cord to power a computer or two, Not a lot of load for a 12 ga cord, but the reel got uncomfortabally warm from the heat build up.. It is not just inductive heat but the fact that air can not circulate around the wires.. If they get so hot you can not hold them in your hand comfortablly worry.
The only time my RV cord has gotten that hot.. Well, it was sunlight, not current, doing the heating. (Actually it was not the RV's cord but the house's cord.. I had a 27' heavy duty cord to power the house off the RV in the event of power fail. Used it too, this day I was using it for something else, sucking peprhaps 5-010 ams on a cord designed for 30-40, and streatched full out (We needed every foot). the shaded part of the cord was COLD to the touch, the sunny part I needed gloves)
Home is where I park it!