I use GIK. You can start with two 2X4 on the first reflection points (1 on left and one on right) and another two in between the speakers. In my room, the 2X4 made a huge difference for sound staging and focus. The 244 from GIK will work fine for you.
Mcloughlin's links above are very useful. Wish I had found them earlier. I had to spend so many hours to get my speaker placement correct. But they are very well in line with that those models suggest.
Mcloughlin's links above are very useful. Wish I had found them earlier. I had to spend so many hours to get my speaker placement correct. But they are very well in line with that those models suggest.