ML Aerius/room tweak

I use the Aerius in a rather large room (30x20x13). The room interaction was producing a +6 to 8 dB peak between 4K and 8Khz. Most of the room acoustic tweaks I'd read about were for the lower end of the spectrum. Recently, I bought some acoustic foam to see if it would help. Until I figure out where to place it, I thought i'd just lean it against the back of the speaker (behind the electrostat). I noticed a change in the sound and measured that the peak was no longer there. Has anyone else tried this?

I'm now debating whether I should just cut the 2'x3' foam to the same width as the ML and just leave it leaning against the back of the speaker (vs. mounting on stand/wall). Any thoughts? What else do I need to consider? I am a newby at this and would welcome any help.

I also removed the woofers on the ML and replaced them after adding speaker putty for improved sealing. This seems to have improved the bass (I have not measured yet) -- or it may just be the case of "experimenter's expectancy"

Are there any other common tweaks for the Aerius? I have the speaker cookbook on order. I am thinking of altering the stuffing to see how that changes the performance of the speaker in the environment that it is now.

Thanks in advance.

Byas