Room treatment can be addictive

@signaforce  I believe the left side is not much of an issue since the first reflection points are so far removed that reflected waves would not be perceptible. For the right, I suggest 242 absorption panels that you can place when listening seriously and store when you are not. Alternatively, a good size stuffed couch with as high a back as you can tolerate placed in front of the windows would likely help. 
Before you go to the trouble of doing any of that, I suggest you try hanging heavy blankets or moving mats in front of the windows at the first reflection points for both left and right speakers to ensure it makes a difference. I would be surprised if it did not.

To determine first reflection points, place/hang/have someone hold a mirror in front of the blankets and confirm you can see the speakers’ reflections at your listening position.

@tcutter Thanks! My L shaped sectional is head high & actually runs along the windows then into the room. Only one woofer is above the couch (R11’s). I had thought about free standing panels… might give that a try.
Follow up question. I put a bass trap in the far left hand corner of the room (about 12’ from the left speaker & 19’ from the right). I could use it elsewhere if not effective there. Thoughts?
BTW, your room and system is GORGEOUS!

@signaforce I think you’re partway there with the couch if it’s in front of the first reflection points for each of the speakers. if you’re saying head high when you’re sitting you might want to add some panels (2 x 2’) on top of the couch while you’re listening. Those are really easy to put away. 
 

There is only one way to determine if that is the best corner in which to put the bass trap and that is to listen there and in the alternative spaces. I imagine no matter what corner, you’re getting some benefit although there is a possibility a lack of symmetry may hurt you. On the other hand, your room is already asymmetric. Only way to find out.
 

And thank you. I can listen for hours on end.

You could also just put some large pillows on the back of the couch. Easy Peasy. Good luck.

I stopped at 30 panels.  Mostly because I have no space for more.