Generally speaking, opposing corners tend to work well.
I'd suggest downloading REW (Room EQ Wizard), and use the room mode simulator to play with positioning of subwoofers to see where you'll get the best response.
Then, get yourself a calibrated mic, like a UMIK-1, and then you can measure actual response in room to verify your sub positioning.
MiniDSP 2x4HD, UMIK-1, REW... The holy trinity for running multiple subs.
Espon 5050UB, 120" screen, AppleTV4k, Harmony Elite, Sony UBP-X700, Pioneer Elite VSX-LX504, Outlaw 7000x, MiniDSP 2x4HD, 2x HSU TN1220HO subs, 2x HSU VTF-15H Mk2 subs, Defintive Technology speakers: CLR2002 x3 for FR, C, FL; BP2x SR & SL; BP1.2x SBL & SBR; ProMonitor 800 x4 height speakers.