What am i missing here? If you only drained the front plug then THAT is your problem. Like said that would mean you have like 8 quarts of oil in your car then the 5. Drain both and make sure you only put in 5 quarts before you start throwing parts at it.
Anyway, if you decide to go this route and fix your problem, put 5 in with a fresh filter or 4 if you don't change your filter. And PLEASE make sure you drain both plugs.