Has Anyone Ever Run TWO Identical Pairs of Speakers ?

 i’m not a big fan of that GR research guy. Some of his techniques like the one where he used hey antenna meter from an old receiver to show you how radio frequencies affect speaker wires was a little goofy. Here’s a Website that I think the author has more chops the good old boy Danny.

But the videos I linked, are very simple, well used methods of measuring speakers. 

There is not much subjective opinion in them. Anyone, testing 2 tweeters mounted on the same baffle, will get the same results as Danny did. 

Anyone can repeat his test, and measure the comb filtering, the loss of high frequencies when 2 pairs of tweets are connected, and the improved frequency response when 1 pair of tweeters are disconnected. 

And as far as the other site you mentioned, you are correct, there is a lot more info there. But Danny's vids are not meant to replace much more technical sources, only to explain to the lay person what the problems are with running multiple drivers.

I am not a super fan boy of Danny's, but I can guarantee, he has probably forgotten more about speaker design, than many respected designers know. Have you heard his NX Otica's? If he is lacking knowledge as you say, he sure did get lucky (by random?), in designing a kit for $3000, that will stomp pretty much any $10,000 speaker. 

I did this for about a dozen years using Paradigm and Polk speakers.  The end result was very nice SQ. The upper mids and highs of the older Polk 5jr speakers added to the lower mids/bass of the Paradigms 7se speakers.
Later tried various speakers to see if I could get the sound I want thru only one pair.  Bought Monitor Audio Silver, Paradigm SE1s...ended up playing them together as individually, each lacked a bit.

While it was an eye sore to look at multiple speakers, I enjoyed the sound.  Today I run 1 set of speakers made by Focal.  Also have a set of Triangles.  Each does well on their own.

Very bad idea. First of all you will only get an additional 3 dB out of it. Worse, you will permanently damage whatever imaging you have. You can split up woofers that way because the wavelengths they operate at are very long but, you can not do that with midranges and tweeters. At shorter wavelengths the speakers start speaking in two voices instead of one. Tweeters have to be no farther than 1/2 inch apart to speak in one voice up to 20 kHz. When you move them apart like you plan on doing you are listening to a choir instead of a single voice and you smear the image and detail.