Welcome to Gearslutz
A few things,
-Face the right short wall.
-Put your mix spot (where you sit) 38% from the wall. I believe that would be 8.36'
-Treat all corners with bass traps with a core of mineral wool or OC
-Treat early reflection points on right/left and ceiling.
see the following page to give you some guidance on room set up.
GIK Acoustics: Room Setup
Glenn