Here's my HT using Def Tech bipole BPVX's for both side and back surrounds. The smaller BPX's on the outer back walls are for Yamaha's "presence" effects channels and another pair is mirrored on the front wall for the front "presence" effects channels. They are 4' down from the 10' ceiling per Yamaha's specs back in the day, so they are too low to use effectively as height speakers. The side BPVX's are placed in between the rear MLP riser seats and the lower secondary seating. The back surrounds are on stands in between seats 1/2 & 3/4 in the MLP recliners. It creates a decent bubble in the MLP. Just need 4 top speakers now. Heading up into my attic to take a few more measurements before I cut four 9" round holes in my ceiling. I have to say that I'm a bit nervous about this.
JVC X750R Projector,Yamaha CX-A5200 Pre-Pro,Yamaha MX-A5000 Amps x2,Yamaha MX-D1 Power Amps x2,Yamaha RX-Z1 (L&R Surround Channel Amp), Oppo BDP-103D BR, Panasonic DP-UB820 UHD, Pioneer Elite CLD-99 LD, Definitive Tech BP7000SC Mains, CLR3000 Center, BPVX Surround Sides&Backs, BPX F&R Presence, DT UIW94/A x4, (Atmos) Martin Logan Abyss Front L&R Subs/Dynamo L&R Rear Surround Channel Subs, Infinity SSW-210 Center Channel Sub.