Priming Bourbon Barrel Porter

I am about to bottle my Bourbon Barrel Porter and was trying to work out how much priming sugar to use.

If I follow the instructions that come with the kit. It recommends 2/3 cup of priming sugar which seems really high assuming you brewed 5 gallons and end up with around 4 1/2 gallons in your bottling bucket.

By my calculations that is 5.36 oz or 1.2 oz per gallon which is 2.8 volumes of CO2 which is way above style.

Looking at http://www.tastybrew.com/calculators/priming.htm it seems like 2.15 volumes of CO2 is a good average which works out at 3oz for 4.5 gallons or 0.7 oz per gallon.

Has anyone had any experience priming this beer and how much priming sugar did you use per gallon?

I went with 0.7 0z per gallon, will let you know how it turns out.