Emm-dee - Does your trailer have a converter, fridge that runs on 120 volts or an electric water heater? If not that may be the difference between your setup and the OP's. With a 100' 12ga extension cord at 15 amps your voltage drop is right at 5%. I try to limit the voltage drop to 3%, but it's obviously working for you.
mrpancho01 - If you need to keep the fridge cold, but can do without the A/C, you could get a heavy duty (12ga or bigger) extension cord and keep the A/C and electric water heater off and it would probably run the converter and refrigerator.
If you need both A/C and fridge, your best bet is to have a dedicated 30 amp (or 50 amp) circuit ran just for the RV.
Salem 29RKSS Pushing a 2500 Mega-Cab CTD!
Gotta go campin!