I tried my first bottle of my first batch of this last night. I don't remember the exact volume I ended with, but it was around 4 gallons. I used a packet of 4.5 oz of priming sugar from my brew store, the amount they say is standard for a 5-gal batch. I don't know the exact numbers, but I know porter is not supposed to be carbed as much as lighter styles, and I had less than 5 gallons. I left some of the sugar out - I didn't use all 4.5 oz - but I don't have a scale so I just eyeballed and guessed at leaving out about 1/5th of the sugar.
Anyway, this porter tastes great, as I expected, but it is way over-carbed. It really makes a big difference in enjoying it. I am mad at myself for making a stupid mistake that made such a big difference. After mashing, boiling, fermenting, bottling it all, etc, just using a little extra sugar at the end made a dramatic difference in the final beer.
So I'm getting myself a scale and never going to 'guess' at anything again!
And I guess I'll just open the bottles and let them sit for 1/2 an hour before I drink them. Won't be perfect, but it'll be better than nothing...