Just a suggestion, maybe good, maybe not:
Try positioning the speakers parallel to the diagonal of the room, so that when you draw a direct line from L spkr to R spkr, the middle of that direct line intersects w/ its perpendicular line drawn from the corner of the room.
This way, at least the reflection plane will be less uniform and angled differently. In my prev smallish living room (15x17) this positioning gave better result.
What Dodgealum said makes a lot of sense, too.
BTW, I think 20" is too close.
Try positioning the speakers parallel to the diagonal of the room, so that when you draw a direct line from L spkr to R spkr, the middle of that direct line intersects w/ its perpendicular line drawn from the corner of the room.
This way, at least the reflection plane will be less uniform and angled differently. In my prev smallish living room (15x17) this positioning gave better result.
What Dodgealum said makes a lot of sense, too.
BTW, I think 20" is too close.