Some of you will read this and go "duh!" but I figured I would post in case someone else made the same mistake.
When figuring out the amount of sugar to use for bottle conditioning I was calculating it based on the temperature it would be stored at after bottling (room temp) and not the temperature it was at the time of bottling.
I've been dropping the temp to clear the beer out so it was only up to around 40-50F by the time I was putting it in the bottles. This was giving me up to 1 more volume of CO2 that I wanted.