Who positions their speakers straight ahead (zero tow in) and why.

My listening living room has one feature that throws another wrench into the equation - adjustable sidewall "vanes" in the form of adjustable room window/door slats - the old fashioned wooden slats that can be angularly adjusted with the pull of a cord. Most of the these "windows" are actually full length so there is plenty of slat real estate to play with. All of the windows in the room then become adjustable sidewalls (and rear walls,) and with the slats in the horizontal position, which lets into the room maximum daylight there is a big sonic difference compared to say the other extreme - all slats closed - or any slat angle in between.

Behind the window slats are double pane gas filled insulated glass windows and doors and this introduces another effect in general. Also, even when the slats are fully closed - making the room somewhat dark - the slats are still ridged enough that reflections are still modified. These old fashioned slatted windows and window/doors are beginning to fall apart, and my wife has suggested they be replaced with fabric covered slats which would probably be more acoustically agreeable to play with

Point is having sound diffusers that are adjustable on the fly does make for more ways to tweak. There is nothing new about this idea. I can think of more than a few audio heads who use slatted windows as acoustic playgrounds, but it was an option that was "inherited" with the home - not purpose built for acoustics. It does beg the question as to how many suppliers of acoustic room panels have some sort of option like this. I couldn't find any online.

My just recently completed Curt Campbell and Jim Holtz designed, "Bordeaux" speakers sound better in all ways with no tow in. 

The in room response is flatter, and they image and create a huge soundstage best with no tow in.

There are actually some speakers that have a rising upper frequency range, that sound better with a slight tow out.

I also use my Thiel CS 3.7 straight ahead, this is how they sound best.

@atmasphere

My room is approximately 14 ft x 22 ft.

The roof is gable: 8 ft at the center, 3 fact the “walls”. The system is aligned parallel to the gable axis.

Is that a “small” or “moderate” room?

I use NO toe in. I had been using toe in for months, but the center was mushy and unstable, the sound bright, the stage shallow. I removed the toe in, and @g2the2nd  the center stage was far more solid, the stage wide and near surround.

@unreceivedogma I'd call that a moderate sized room.

Some speakers have tweeters with lobes that make the best listening when the speaker isn't pointed directly at you. Every speaker is different...