Position chromatic notes in 1/3 note head size instead of 1/2

[Robert Mengual]

Hello everyone,

I am trying to position the notes of my custom music notation as in the 
screenshot.

I tried using a custom callback for staffLineLayoutFunction. I thought it was 
going to be enough, but it won't allow decimal numbers.

Does anybody have any idea how I can implement this behaviour? Find attached a 
Tiny.ly as well.

Robert

#(define staff-line-layout-callback
   (lambda (p) 0.33
 ))

\new Staff \with {
    staffLineLayoutFunction = #staff-line-layout-callback
} \relative c' {
  c4 cis d dis e eis f fis g gis a ais b bis c
}