Fingering and slurs

[Noeck]

Hi,

I am transcribing piano music and I see a lot of ugly situations with
fingering and slurs.

Lilypond seems to draw the slur and then puts the fingering on the
inside if there is space and on the outside if not. From the score, I am
reading, I deduce these rules:

- fingering above the slur at slur tips
- fingering inside the slur otherwise
- fingering is above the staff for c'' and higher notes and
  inside the staff for lower notes

Is this a general practice or just happens to be what I see here?

I can regularly switch from avoid-slur between inside and outside and
set staff-padding to ##f and revert it by hand. But can you give me some
hints how to implement the rules above? I.e.

1. change avoid-slur based on slur beginnings and endings and
2. change staff-position based on the pitch of the note?

MWE:

\relative {
  \time 3/4
  \tempo "default"
  b'4.-2( a8-1 cis-2 e-4) |

  \tempo "inside"
  \override Fingering.avoid-slur = #'inside
  b4.-2( a8-1 cis-2 e-4) |
  \revert Fingering.avoid-slur

  \tempo "what I want"
  b4.-2(
  \once \override Fingering.staff-padding = ##f
  \override Fingering.avoid-slur = #'inside
  a8-1
  % I know this looks bad, but I that is the best rule I could find
  % \override Fingering.staff-padding = ##f  % manual override
  cis-2
  \revert Fingering.avoid-slur
  e-4) |
}

Thanks in advance.
Joram