Thanks for your reply, but unfortunately the value of Beam.gap depends on how long is the measure, then it requires to be set only after a definitive score and with a trial and error procedure...
BTW, I wonder if these issues are reported as known bugs in the ML
When tremolo beams between whole notes don't work good, try to specify directions of implicit stems of whole notes.
%%%%%%%%%%%%
\version "2.22.0"
upper = { s1 s }
lower = {
\clef treble
\override Beam.gap = 3 % a way to fix 2)
\repeat tremolo 8 { \stemUp c''''16 \change Staff = "upper" \stemDown c''''16 }
\break s1
}
\score {
<<
\new Staff = "upper" \upper
\new Staff = "lower" \lower
>>
}
%%%%%%%%%%%%
If you want to improve the beam slope, probably overriding beam positions is needed.
Akikazu