RPG Skyline mounting on ceiling

(Somewhat off topic, yet relevant) I had my entire room's ceiling sprayed 1" thick with bleached-white cellulose insulation fiber. This is the same gray stuff found on warehouse ceilings, etc. It improved the echos & reflections considerably & was not very expensive, although it was quite a messy install. The cellulose worked well enough that I didn't have to completely hide the beautiful hardwood floor under full carpeting; a large wool deco. rug centered in the room does nicely. Also hung some artwork and various hook rugs on the walls all around, plus the curtains & stuffed furniture all ads up to some pretty decent room treatment and looks quite natural compared to the various treatment contraptions. I still do need to bass-trap one troublesome corner reflection though.

Hi Gregm will now try to answer your question ... (we've been away for holiday so I just got back online). I'm no expert regarding room treatments, but this one corner with boomy bass is apparent as I walk around the listening area. The bass accentuates when I approach the front lefthand corner of the room, and is also somewhat peaky at the left rear corner. Righthand side doesn't behave that way at all, as the room is asymmetrical. I'm stuck with speaker placement as-is but wouldn't want to change that anyway since I tweaked it for staging properties.
I think I need to experiment with a corner tune or a tube trap device or two, but haven't yet researched my options or educated myself regarding various posssible appproaches to fix. Roomtunes I am aware of too, but don't have space for those in our combo. listening room / living room area

Gregm thanks for the great idea! Also much appreciate your referral Kitch. That corner has always bothered me as there is a curtained window in the way. I never even thought of mounting "on the sidewall next & slightly behind the spkr." that's just a fabulous suggestion.
This is such a perfect example of why we should participate in the forums; you never know when someone is going to come up with a great suggestion / solution (to my offhand comment) & I wasn't really even seeking answers, so this is such a pleasant surprise! thanks again y'all!