Cool, not really sure how you would do a drop ceiling with plywood but if you mean standard two layers without clips the performance is pretty well documented for sound isolation ( much less at lower freq), for in room response I think the clips are very important for the flexing action. I think the key is moving mass, so without the clips you still have the mass but much less movement.
Pre-Pro: Emotiva XMC-1, DSP: Mini DSP 2x4 balanced
Amplifier: Sunfire TGA7400, Lab Gruppen FP10000Q
Speakers: JTR Noesis 212HT (LCR), JTR Slant 8's (surrounds), 3 Orbit Shifter LFU's
Sources: PS3, HTPC, Dish Network
Projector: Epson 8350
Screen: Seymour XD AT 138" diagonal 16:9