Intonation

I would like to open up a discussion on the challenges of keeping chords in tune, especially in higher positions and when there is horizontal stretch across strings or vertical reaches, or, in general, where strings might be deflected horizontally causing them to shift in pitch. I am working on a piece (Poulenc’s sarabande for guitar) and find the open-voicing of the chords really reveals any intonation issues. Are there recommendations for working on keeping the fingers vertical and the notes in equal temperament even in such cases? Etudes? Technical exercises? I’m thinking “the spider” for horizontal finger work, or Tennants fixed finger exercises focus spider on intonation (though the resulting intervals are sometimes dissonant making it less noticeable when notes are out of tune)/