Thanks for your comments, Karl!
Vn 2's leap to an octave with the va in m. 25 seems a bit jarring.
Yes, and that sudden starkness is the effect I want.
In m. 83 vn 1 leaps down a Major sixth, crowding vn 2, so that the latter's Db "passing note" thus becomes a unison
Yes, it's a suspension resolving to a direct unison. There are a number of such cases, but they don't really bother me. I was not trying to follow the rules of counterpoint strictly.
In m.164, the violins swap tones which has something of a static effect.
Indeed they do, and that's also intentional there.
In mm.10-13 modify the slurs in vn 2 (e.g.) for the strings, the slurs coincide with bowings, so you shouldn't have a bow change mid-slur (as in m.12)
This is a hack for NotePerformer. The slur will NOT extend across the bow change in any score I submit for performance, but if the slur is broken there in the Sibelius score, NP plays the vln 2's E-flat as if accented - VERY wrong.
I love the "crunch" between the violins in m. 155 for instance
Thanks - I like that suspension too.
What do you think about having some passages played by a a quartet of soloists (rehearsal mark N for example) for textural variety?
I've actually been thinking about that, or even rescoring the piece so that it includes some wind soloists. Will probably never happen, but I agree it's a good idea.
I wonder if from m.423 to 439, the dynamic markings may be rather numerous and fussy?
Again, these are hacks to make Sibelius/NP render the passage with the expression I want. I agree, they're not needed in the finished score as human players will supply the expression naturally.
Somehow, the "direct octave" between vn 2 and the vc at the cadence into m. 595 jumped at me. What do you think?
Your ears must be better than mine, Karl. I don't hear a problem there.
mm. 613-16, cast the vc in tenor clef. Also mm. 701-06.
Done, thanks!
m. 711 another harmonic/textural "crowding" moment between vn 1 & 2. Also the parallel unison from mm. 768-69.
Agreed on m. 711 - I'll have to find another solution there, thanks. The parallel unison is intentional, to emphasize the last 2 notes of vln 2's phrase - also helps introduce a bit of confusion to the texture there, which is what I want in that buildup.
Overall, very well done and richly rewarding. Congratulations!
Thanks!

My immediate thought after my first listen yesterday was that it feels too much the same texture for a great deal of the piece. My first thought was to suggest an occasional break ... but then I saw your designation unbroken in the score. Having solo quartet for some passages, and more use of pizzicato would be my suggestion.
Yes, I have had the same thoughts and will give those points some more consideration. Again, many thanks for listening and for the VERY detailed comments!