I hear ya, near tapped out myself. I'm gonna put down a floor and then play a bit of jazz on the walls. Leaving some things unplanned makes life more interested."tap...tap..." okay, I've officially tapped out of this thread.
Stand by what I said, agree with Highbeams comments as well.
You obviously have your mind set on what you want, you asked about the floor joists, question was answered.
I would however really like to see a picture of the long narrow tall shed once it's completed.
Good luck!