Changing accidental size and alignment in chord symbols

[Lib Lists]

I'd like to change the size of the accidentals and their alignment in
chord symbols.

Here a MWE:

\version "2.25.5"
\chords {
  aes2 cis
}

Specifically, I'd like to have all the flats smaller, and the sharps
smaller and horizontally center-aligned with the root note name.

I checked the manual and the mailing list, but I wasn't able to find a solution.
Any help would be really appreciated!

Cheers,
Lib