John, I wish I had that kind of width to work with. My current two car wide carport, which will be replaced by the garage, is 19' 6" wide on the inside. I checked my brother's two car garage in the same community, and it is a little less, at 19' 1". Maybe that is the standard here in AZ. I could probably expand mine by another 3-4 feet without making the house look too narrow, but would still be walking sideways in the garage without moving cars out first. I am looking at a 4 post lift, as one of my classic cars is almost 21' long.
My calculations are: Current RV - 9.92' with mirrors, and a lift with outside post width of 9'. Add the two and I'm already up to almost 19' overall width, with the RV mirrors scraping the wall on one side, and the lift on the other. And the far side of the lift will be 6" from the opposite wall.
By the way, love your garage!