I did get to test the center seat. I would estimate that a 6' person would fit, but not by much. There was an inch or two above my head at 5' 10". Maybe some others can provide exact experiences of hitting their head and what their height is. The rear seats for me had about 4 or 5 inches of room to the glass hatch window. The seat is comfortable, but the protruding side wheel well doesn't allow for a small arm rest and the experience is like sitting next to another person (except the plastic wheel well is not as forgiving). Perhaps a third party solution of an additional armrest on each side that doesn't stick out further than the bottom of the wheel well could be offered. The challenge would be lowering cargo capacity by a small amount if a arm rest was installed. The rear seats require that the 2nd row is properly positioned for leg comfort. If the 2nd row is too far back, then sitting on an angle with knees and feet toward the center seat area can work, if the center seat is moved forward (or missing in the 6 seat interior). Having the center seat moved forward could be uncomfortable for the two outside passengers in the 2nd row. UPDATE: Just got finished looking at the 2009 Escalade. Surprise! The rear row seats 3. Silly me, I keep the rear seats down, so little did I realize it fits seven adults (if 3 are trim). So why add this data, to inform you that the second row of the Escalade has 15 inches between the 2 seats and only 9 inches when including the raisable arm rests. Yet, I can get to the back row nicely through that empty center space. I look forward to check the difference of climbing in the back of a 6 seat Model X with the 2nd row moved forward or through the center space with the seats in a normal seated position. There is far less head room in the old Escalade in the 3rd row than in Model X. A total of about 49 inches of width for the 3 seat rear row; tight for 3 passengers. However, there is plenty of space above the wheel well in the Escalade to shift the shoulders into. It is easy to place the arms on the flat surfaces above the Escalade wheel wells. Model X has the continuous curve of the wheel well that caused my arm to slip down. It was more comfortable to just keep my arm on my lap. Maybe a folded charcoal gray towel could make the difference when attempting to place the arm on the wheel well.