Lucky you if you have a 9 foot door. Most garages have an 8 foot ceiling, unless the garage is considerably lower than the house floor level. That leaves 8 feet to fit the header, a 4x12 spanning 16 feet or so over the opening. So most doors are 7 feet high at the opening and even less below the door if it swings up under the opening. Roll-up doors can rise up above and behind the door opening but not solid wood doors.
If you limit the lift or travel of the tailgate then it won't rise far enough to clear a 6 foot tall person. I have trouble with that when I open the tailgate under my garage door. It's high enough to be out of sight but low enough to smack you in the forehead when you walk into it. Ouch, that hurts!
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2015 T4R Trail Edition w/KDSS. Baja Rack flat utility rack, Baja Rack ladder, WeatherTech floor mats, Demello rock sliders. RCI skid plates, Falken AT3W LT285/70R17 tires, ICON Stage 7 tubular 2" extended travel lift, ICON Rebound 17x8.5" 0 offset alloy wheels, Baxter Performance remote oil filter adapter. Side exit exhaust, 2nd recovery hook on rear frame corner, DIY wheel well liners with 1/4" neoprene rubber.