my room is not as long but given your width and MLP preference, and other parameters ,I solved my rear and side mounting like this;
I penciled the problem a while and got this: 2 eight foot track light bars, one end anchored to the walls and then in a dihedral sorta angle to give the possibility of equidistant surrounds and rears (from MLP). I searched around for track light fixtures (USED isok, its the hangers thatr need to be ok) and " removed " and reconfigured the susupension part that fits into the bar (you'll need to extract most of the innerards and keep a sectiion of the rubber isolator to provide proper retention). So then i fabricated an appropriate rube goldberg to give me a good attachment for the speakers. I had to beef up some attachement points to retain swivel and angulation possibilities. I ran the wires thru the ceiling ( my home-my way). I painted the rack light bar and the hangers light primer grey. I used a plate and 2 each toggle bolts to hold the central ends , separately .
My surrounds are Klipsch RS3S and the rears are Klipsch SLX. The rears hand down about 15 inches from the ceiling but i "stretched" the hanger for the surrounds and have them down in the range normally suggested to height and angle WRT listening level at the MLP.they are very close to the wall so the extra "hang" is not a problem.
there seems to be an issue with with attaching the photo but i'm willing to address the porblem, just right not today, it "super sunday" duh!
Denon X5200 , Emotiva UPA7, for 7.3.4 ATMOS/DSU
Klipsch FL/FR: F3 , Center: Icon 25 , SL/SR: RC3II , SRL/SRR :Icon 36 Towers, TF & TR: SLX
2 30" BF THTLP'S and SUBMAXIMUS and Inuke6000DSP
SHARP 80" LED/LCD, Xbox1 PS4 Panny BD 220