I have been able to play around with my speakers this week and did end up with the following setup.
Distance to side walls >50cm (1.6 ft), distance to back wall 120cm (4 ft), distance between speakers 223cm (7.3 ft), distance from speakers 268cm (8.8 ft).
I did notice that the speakers don't rely like sound absorption. It can help with sharpen up the sound image at a smaller distances to the back or side wall, but it kills the magic when placed at 120cm (4 ft). I wonder if people have tried different type of diffraction panels with these speaker and to which result?
But here is the thing, what is actually happening at 120cm (4 ft) from the back wall? 120cm (4 ft) in the speed of sound is 3.5ms, this x 2 for travel to and bouncing back from that wall is a delayed reflection of 7ms. But I got this info from the Audio Physic web site saying the following; "The spatial information relating to a sound source is mainly detected by the brain in the first five milliseconds, everything which follows will at first be ignored. Sound travels at 1.7 metres (5.6 ft) in five milliseconds. If the sound of a reflection has to travel 1.7m (5.6 ft) more than the direct sound of the source, then it will have no influence on our spatialereception." But this 120cm (4 ft) distance does make the sound more airy and gives a more real ambient presence.
Placing the center at 120cm (4 ft) from the back wall is giving me better results as well, but the effect is less due to it being a mono channel.