How best to shoe horn speakers into a room

If the horns are time aligned and the radiation pattern is appropriate you can put a fairly large horn in small or med rooms and use in near-field if wanted. If alignments off you need greater seating distance if radiation patterns wide you may have issues with reflections off side walls. I can run any loudspeakers I like and I still end up with massive horns in my office system. Nothing else I have used is as full and detailed at low levels nothing else is as non fatiguing for greatly extended use why I use. At this time systems a pair of community leviathans with 4x altec 515b and  giant rare community multicells with tad 2001 I also run a sub bass system. I have this systems radiation patterns matching and all time aligned for listening position I can sit as close as 5 ft rooms 13x17 the horns fit in my corners and take up little use-able floor-space less than any of my monitors on stands.

OP ?-As the room to speaker so called ‘fit’ is deemed to be quite significant, how do you measure, adjust, determine, your present speakers would fit, or how do you go about projecting any upcoming desired speaker can, will or will not fit in the space you have for it, in advance?    Having a basic understanding of how loudspeakers function how rooms effect such and massive hands on experience. 

@blindjim

I feel too much of what we know of fitting speakers to a given room size comes only from experience, although this logic appears to be somewhat contentious lately.

Any so-called "logic" that doesn’t come from experience when fitting speakers to a given room size, I’d rather be without - generally speaking.

Does this “speaker to room ratio” claim, merely serve to further a mythical audio-nervosa proclamation?

I don’t believe in a schooled thought here that would more or less rigidly dictate a given speakers size to some "fitting" room ditto, whatever that means. I’ve had small 2-way stand-mounted speakers posing much bigger problems with proper room integration than large, floor standing speakers in the same mid-sized room. It mostly comes down to the bass and lower midrange character, and how the used tuning "hits" the room here. Looking out for speakers that gets the all-important upper bass to lower midrange energy right will save you loads of problems, to my experience, and help further the integration with the rest of the central to lower bass. There are other aspects to look for, as has been pointed out by others here, but I find this to be a particularly "touchy" area to get right. Indeed I’d go on to advocate for a sub (or two of them) in this regard, but that’s another subject I guess.

Where are the priorities? Distance to side walls, from the front wall, stay so far from the ceiling, maintain at least this much separation between them, ‘golden’ triangulate the speakers to the LP?

That’s very much subjective, I’d say, but to me a smooth sonic "sphere" going from one speaker over the middle to the other is vital. From here I prefer sitting on the edge of or slightly within this sonic sphere. Having the sphere too far in front of me gives the sensation of music happening "over there;" too much within it can feel slightly imposing. Mono recorded music is a nice tool for this dialing-in, as it can easily sound disjointed or too dense when the speakers aren’t placed properly. I don’t go by the "golden triangulate" as a rule, as generally here I find the speakers to be placed too far from each other (in relation to my distance from them) to give the proper, smooth center-to-the-sides fill. But obviously speakers are different, and so may be your preference compared to mine.

As the room to speaker so called ‘fit’ is deemed to be quite significant, how do you measure, adjust, determine, your present speakers would fit, or how do you go about projecting any upcoming desired speaker can, will or will not fit in the space you have for it, in advance?

Listening to the speakers in any given environment gives me an idea of their sonic signature per the above. I listened to my current speakers at their maker who had a similar-ish size and proportion room compared to my own, but apart from that I had a clear sensation of their prowess in the upper bass to lower mids, their dispersion characteristics, overall driver integration, and in this regard also a feeling of the distance I needed from them. They roll off below some 60 Hz, so that makes integration easier.

Lastly a word on "room equalization." I’ve always refrained from heavy absorbing, as I feel it kills the sound when overdone (and usually that doesn’t take much, to my ears). Diffusion is more my thing. I use a light amount of bass traps - they can really do wonders, and not only in the bass. From there I prefer natural material and regular interiors; book shelves, some other furniture, maybe some textiles on the walls to break reflections, and a cow skin on the (wooden) floor.