My room is almost similar to yours. You need to experiment with the distance between speakers as some speakers sound better closer together(away from side walls) while some speakers sound better further apart(close to side walls). My current speakers need to be further apart but are limited to the width of the room. Fortunately they can be placed close to side walls which are treated with diffusion and absorption panels.
As advised by Shadorne, your suggestion of placing the absorption panels so that the middle section meets the tweeter is appropriate. The same advice has been given by Ethan Winer of Real Traps in his forum pages.
If you have extra pieces of RPG diffusors, try placing them directly beside the speakers on the side walls apart from placing absorption panels at first reflection points. The soundstage will be more even and wider creating a more expansive, enveloping and natural sound.
As advised by Shadorne, your suggestion of placing the absorption panels so that the middle section meets the tweeter is appropriate. The same advice has been given by Ethan Winer of Real Traps in his forum pages.
If you have extra pieces of RPG diffusors, try placing them directly beside the speakers on the side walls apart from placing absorption panels at first reflection points. The soundstage will be more even and wider creating a more expansive, enveloping and natural sound.