Lmr, I agree the speaker needs to be angled down pointing toward your listening position, so if you can build and mount a shelf to the ceiling, making the speaker secure is not a problem. Use a lip on the front of the shelf as Zd542 suggests, and the HTM2 has threaded inserts in the bottom that you can also use. These were used to secure the speaker to a stand. See 7b in the owners manual for "FS HTM" listed here,
http://bwgroupsupport.com/manuals/bw-archive
You can find it in "800D Series" or "Nautilus 800 Series"