subwoofer suspended from ceiling?

Not a good idea from a structural vibration point either.
I think within time you would be listeing to your roof, rafters and walls rather than the sub.

sounds like i am committed to the experiment.
get back to you in a week or so.

We've done a number of designs with soffit mounted subs. There are issues, vibration, making a very rigid mount, but if you can over come those it can work well. In most cases the floor is simplier, and it's what most people do, but it doesn't necessarily mean it's best.

The 1/2 between floor and ceiling as Eric points out can sound very good. It cancels out the height mode which is typically the dominant axial mode. We do this regularly in our designs

Committed is what you should be for doing.Save that suspension for monitors or turntable on rigid pole.But Put this up so I can easily follow what happens.I am thinking of that scene in Young Frankenstein when they have to crank the table up to get the lightning.
G'Luck.
Chazz