No matter how big you build it will never be big enough.
I have a 40x60 with 12'6" ceilings. Across the back row I have four -four post lifts and one two post lift. Floors are epoxied. I have three doors - two 16' and one 12' in the middle. When I first bought the building My dream was to have a show case garage. The dilema is - if its a show case you cant work in it properly and if its a work shop you cant park your babies in it without getting everything dirty. Also by the time that I got all the lift s intalled to increase capacity it looks so crowded that the "show" quality of it is pretty well diminished. I have a capacity of 16 cars Back row f on top and five below, front row six across. I installed all the requisite air lines, power, reels etc but it has a confused identity. I think that what I I really need is one garage for finished cars and one for working on projects and a seperate for storage of whells tires parts etc. They need to be seperate buildings. In the show garage I would not double stack. it looses too much asthetic.