Room setup 101
Make sure the speakers are throwing down the room the LONGEST way. If your in an 8 by 11 room - your speakers should be facing.. if possible... so they are firing down the 11 feet. If the glass you mentioned is at the end of one of those long runs - try to face the speakers the other way so they are not firing into the glass rear wall. If they are - cover the glass surfaces - somehow - with a blanket - or even some of those cool panels you bought.
Stay away from any dimension that is divisible by 2.
Your speakers should not be at 50% height... they should be right where your ears are.. which is usually a little less than half. Your seated mix position should not be 50% down the room (where usually the largest cllection of nodes and or standing waves collect) it should be at 38%. If your firing your speakers down a 10 foot room, that means your head (ears) should be 3.8 (45.6 inches - 10x12=120 inches x.38=45.6) feet away from the front wall. Now - build a perfect triangle based on that 38% position. Both speakers should be pointed directly inside the triangle at your ears.
Now that you know where your sitting, and you have your speakers setup - - sit there. Hopefully - you now have a symetrical mix environment... with this triangle placed equilaterally between the right and left walls.
Have a friend drag a small mirror along the LEFT wall untill you can see the cone of the RIGHT speaker in your peripheral vision. That is where your first reflection from that right speaker will be (assuming your sitting in the mix triangle at 38%) Thats where your first sound panel should go. Do the same to the other wall. The 2nd main source of trouble from reflections is the rear wall - and could typically benefit from panels that are at the same height as your speakers.
The 3rd and most overlooked place that needs treatment is behind your speakers. More than likely theres a great deal of bass and low mid buildup. You can purchase bass traps, or make them which is typically cheaper... and you get to pick cool fabric colors!
I hope this helps