What could be instead of side walls?

Zaikesman, I was stretching a bit on that second point. Depending on the back wall and front wall distances, the side panels might make a positive difference (would have to work out all the ratios), but I'm with you and would do that as a last resort. Marakanetz, move the speakers as close together as you can w/o messing up your TV -- every little bit helps. By the way, I'm assuming you don't have the TV or anything else in between the speakers -- that would, as I'm sure you know, also mess up the soundstage. Good luck.

Good points made here. Of less importance, but I would also add that vibrapods are not a stable mounting base for speakers and will allow them to wobble and vibrate more.
My speakers seemed to get better once a fixed a short spike and the speaker sat firmly on all 4 spikes.
Mapleshade Records recommends 2" diameter brass cones to transmit vibration out of the speaker. You could use granite, etc. blocks for the brass cones to sit on.

You are perfectly correct as far as that goes, Cdc - and that's just the problem, when it comes to springy suspended wooden floors. Many speaker manufactures will specify in their owner's manuals that the spikes should be omitted in cases like this. Rigid coupling of the speaker to a non-resonant substrate, such as a poured concrete foundation underlying a carpeted first-level floor, is of course the ideal situation. But when it comes to a flexible, resonant floor like the one Marakanetz seems to be cursed with, attempting to break the mechanical coupling is about all one can try to do, as it will sound better this way even if it means the speakers are then not quite as rigidly positionally fixed in space while the music plays (which they wouldn't entirely be anyway, if the floor they were fixed to was flexing along). You do not want this type of floor acting like the soundboard of an acoustic stringed instrument, with the speaker's drivers as the strings, and the cabinet spikes as the bridge. You've got to attempt to "float" the speaker in this case, at least with near-full range floorstanders . (In my old apartment [and it was literally old], I used to fantasize about rigging up some kind of hanging cable harness to suspend my floorstanding speakers from the ceiling! Lucky me, now that I have the system set up in my new digs on a foundational substrate - when I finally decide on my speakers' ultimate positioning, I'll even be able to actually use my spikes!)

Cdc's, Rive's & Zaike's points are well taken. I faced a similar situation at a friend's house, trying to place Avanti 3's. Our fortunate difference was the floor, where the wood lay directly on concrete. I.e. we had no real suspension, but instability, as the floor wasn't level -- let alone the side walls that are outward looking to the listening position.
To make a very long story short, we came up with a compromise:
1) Speaker support: factory supplied bronze (I think) spikes for speakers on THIN granite, granite on 4 Nordost Pulsar points, Pulsars directly on wooden floor (it was hell getting these level!). BTW, Jadem has been experimenting with equip support for years now, and knows his stuff. Can you alert him?
2) Placement: far apart (!) and toe-in at around 75 degrees. Alternatively, we tried them parallel and closer (@6 ft) -- but that meant going back further for an image, into the corridor (no cigar).
This ain't perfect, but it's reasonably acceptable in a grand orchestra with voices (Mahler 8 -- around 900 people orchestrating).
Don't know if this helps.
Question: can we all come up with an idea for placing Mara's speakers in free space? Then, some of us can suggest the right speaker support. Cheers!

i have a sin to place a tv between the speakers but that's where i have my whole point viewing ld-music video collection that i have. also viewing vcd and dvd music videos as well. so tv should stay between.
the equipment stand is also standing next to tv between the speakers. so the only thing i can arrange right now is to remove the equipment stand from the inner space and run longer ics to amps thus "clearing" the objects standing between the speakers.
did anyone try to get a granite slabs from the monument shop?:^)