The per se very solid and flexible fixture has a gavierenden disadvantage: It is just for hobbyist when it is bought for the Acer H7531! Since I had no desire to return the thing again, I bought at the hardware store fitting bolts (M3x20) and matching rosettes. So you can then mount the H7531 to the mount and the theater experience is nothing more in the way.
Those who want a 100% perfect solution, should stay away from this article!