[William Miller]

How far have you gone with this? My suggestion is that you make it wider if you can. 20' is a little narrow I'd go 24-25 if you can.
Mine's 25x32, just enough room by the time you put benches and cabinents arround the perimeter. It won't cost that much more and you may like it. I have an 8 12 roof to match my house and the attic floor is 12 x 32 head room is tight so going 10/12 is a really good idea.
I put some steps to the attic after the inspector was finished.
I put in 100 amps which is more than enough. I have electric heat and I put a window banger thru the wall. My problem with A/C was that although the walls and ceiling are insulated the wooden roll up door is not.
I got condensation on the outside which swelled up the masonite panels.
Another project is to insulate the door which will also help a lot in the winter. If you can get a metal door. Mine is wood because again, I wanted to match the house.
Good luck!