Showing fingerings in front of slurs

[Paul McKay]

Hi
I want to show fingerings in front of slurs in a manner very like that
demonstrated in the "Using the whiteout property" snippet

This is what I've tried:
\version "2.24.0"
\language "english"

\relative {
        \override Staff.Fingering.layer = 2 % fingering should overwrite
slurs
         \override Staff.Fingering.whiteout = ##t
        r4 r8 <fs''a>-1-3( <g b>16-2-4 <a c>-1-5<as cs>-2-4<c e>-3-5)
}

but the fingerings still avoid the slurs. I want them to appear just where
they would if the Slurs weren't there at all.
What am I missing?
Thanks
Paul McKay