The bolt point on the ceiling bracket is 5.375" below the ceiling.
The QS8 is 8.25" high, and (judging from the picture) the bolt point is about 1/3 of that height from the top.
Therefore, the bottom of a QS8 mounted with this bracket will be slightly less than 11" below the ceiling.

If your ceilings is the standard 8' high (is that even standard anymore?) then you'd have to be over 7' tall to run into it.