I'm not speaking for the acoustical engineer, however the decision on the crossover frequency is not made in a vacuum. All the raw anechoic curves from each driver are taken into account - both in and out of the cabinet. Then the search for the smoothest response, both on and off axis, takes place. Different filter topologies are investigated -- in a computer model, in the anechoic chamber and ultimately by ear. Harmonic distortion measurements are also considered. Raising or lowering the crossover frequency a bit can pay big dividends.
The slight difference of 350Hz (1750Hz vs 1400Hz of the RF-82 II) could be attributed to the differences in the hybrid horn or the new cabinet shape or both. Or something else entirely.
Keep in mind that a crossover is not a brick wall, there is a slope; for a 2nd order filter it is 12dB/octave.
At the frequency of 1750Hz (roughly = A6 -- the A above A above A above middle C on a piano tuned to A440) 350Hz amounts to 4 half-steps or 4/12 of an octave (=1/3 of an octave), i.e. a major 3rd (or F6) -- which is barely any change at all in the grand scheme of things. To your ear that would be a change of a bit more than 3dB at 1400Hz - again not much in terms of sheer output (the output from the tweeters would now be a bit more than 3dB less than it was before, however it is also half the power going to the tweeter at that frequency. Perhaps 1750Hz created the best response, perhaps overall distortion was reduced, perhaps both. Or neither, and it just sounded better that way.
Can speakers be too big for a room? Physically, they might take up more space that is available, but acoustically, it's more about the seating position and where the walls are... The crossovers are designed, generally speaking, with a 3m/10ft listening position distance in mind. If you are seated very close to the speakers (say 4-5 ft away), then a very large/tall speaker could be at an acoustical disadvantage to a smaller bookshelf with a well-integrated sub (w.r.t. crossover freq. and phase). In a smaller room you will also have stronger reflections (the walls are closer to the speakers and your ears, inverse square law, etc.). With a large speaker you would be tempted to sit further away for best driver blend, but that puts you closer to the rear wall which increases the amplitude of the reflection off the back wall. In a small room you might sit closer to the speakers, the walls are further away, meaning the reflections are attenuated (inverse square law), and you are half the distance to your speakers. So that means it would make up for... let's see... half the distance is four times the sound power or amplifier power, i.e. = 6dB worth... and can make up for the size difference in speakers, loudness (perceived output from the speakers), or amplifier power.
Chuck Hawks in an interesting guy... he is not shy about sharing his opinions (he writes about guns too so I'm quite familiar with his stuff).
This comment is very interesting...
... because in some cases it can very well be exactly the opposite.
