Yes, the head room lost is around 6 inches.  Depending on how tall of a door is how much swings inside.   So the taller the door the farther the first rafter has to be set back.   We didn't do it far enough on our second building I think because of a miss communication on how much room was needed.  Ended up just reconstructing the first rafter by raising the bottom cord up a foot. Worked fine,and would need to do the same if the ceiling was going to be finished.   I am not sure they would work on a side wall unless it was a couple feet shorter then the sidewall.