We've been in this house in San Juan Capistrano for approx 19 years. We have experimented with different speaker positions over the years but are satisfied with where we ended up, sitting a foot away from the rear glass wall. As a result the there is 26' behind the speakers, the speaker position is quite asymmetrical, the RHS speaker is 5" in front of the L speaker, but the speakers are perfectly in phase. To check this we play a SonoruS 5.1 15ips 2 track tape that originated from a multichannel DVD-Audio or SACD and mixed in the analogue domain back to 2 channel. The result is that you have a sound-stage that completely envelopes you; on Kraftwerk's "Maximum Minimum" you get the crowd noise behind your head.
There is no room treatment; we have useable bass measured down to 12Hz with the Giya G1. On the ground floor the room measures 40 long by 31 wide by 23' high. On the upper storey, there is a open dinning room that over looks the great room. So I guess it must be approx. 60' x 31' on the second level, including the balcony.
With smaller speakers such as the Avalon Eidolon, we reverse the speakers & listening room, using the glass wall for some bass reinforcement. Back in the day when we were distributing Halcro, we used to borrow different speakers every year for CES, so we had a chance to listen to some fabulous speakers for a couple of months, while they broke in, such as WIlson MAXX, Focal Utopia, Eggleston Savoy... The best $$ value were probably the CAR T3.1 horn speakers, while colored, remarkably fast & a huge amount of fun.