Well I guess I don't need to tell you that a squ room and being set up in the middle is about as bad as you can get.
Needless to say you are just going to need A LOT more bass trapping in that room then you are planning and make sure you place that panel off the wall 4" on that back wall. In fact you should go with more panels back there if you can. Also you straddle corners where that are not just wall to wall corner but also ceiling to wall and floor to wall. See the following for a panel straddling the ceiling to wall.
For the ceiling us 2" panels spaced off the ceiling 2" and cover the early reflection between where you sit and the monitors.