+1, as high as is safe, tilted down. Tilting directs the sound at the audience instead of the ceiling. Up high makes the sound pressure slightly more even from the front to back of the room, e.g. instead of standing in front of the speaker 1 foot away and getting blown away, the speaker is 5 feet over your head and you are receiving a lower, off-axes sound pressure.
For starters, tilt so a line coming straight out the middle of the horn hits the middle of the audience (or the most important part of the audience) at ear level (standing or sitting), or wherever you want the 'best sound'.
Optimizing the tilt is a little more complicated because it depends on the actual off-axis response of the speaker, few speakers output a uniform frequency range over the specified horn angle. But a 'tilt to the middle of the audience', followed by walking around and listening will help you adjust the tilt.
There are some fixed-position cabinet tilters out there, and a few adjustable ones. This one is the absolute best, because it maintains the existing center of gravity, but it's not cheap compared to the others.http://www.bt-12.com/
I replaced the pole cup that I previously had in my sub with a screw-in base and rod from K&M (this has a metric M20 thread on the base and pole). The difference in stability is night and day and I'd never want to go back to a pole cup on both ends. K&M makes both a fixed rod and an adjustable rod, but neither has a "short" setting and you might have to have a machine shop mod it for you if the height is too much for your app. We played an outdoor pavilion a few months ago and barely made it with the clearance. Here are the K&M parts #s
K&M 21337 Adjustable distance rod (36"-57")
K&M 21334 Fixed distance rod (31-1/2")
K&M 24116 Speaker cabinet connecting plate
They also make a crank up adjustable rod, but I suspect it would be much more difficult to modify if it needed to be shortened.