Yeah, knowing your height, sans people, is a must. I used a 4’ level on the highest point (middle of front crossbar) and, making sure the level is level, measured from the underside of the level to the floor. I am at 6’5” and change. I use 6’6” as my height and put a sticker with the height inside the 12 volt cover on the dash. Then you need to decide your tolerance for clearance. I have parked fine in a posted 6’7” garage, but keep your eyes peeled.
I've seen a few parking garages be a little off on their measurements, so having that extra inch or two sure helps!
I had 9" lift on my truck years ago and I cut off the antenna just above the height of the cab