How to deal with Time Signatures horizontal alignment?

[Valentin Villenave]

Hello everybody,

In the following LSR snippet (which I added a few months ago), time
signatures are printed above the staffgroup, which is really useful
for large orchestral scores:

http://lsr.dsi.unimi.it/LSR/Item?id=272

However, as you can see in this snippet, I had to add the following line:

\override TimeSignature #'extra-offset = #'(-2.2 . 0.0 )

otherwise the time signatures were still printed on the right of the
barlines, which was no longer convenient since they're printed out of
the staves.

I'm looking for a way to do this automatically without having to find
the right offset by myself (in case, for example, I need several
TimeSig contexts in a score, with different fontsizes).

What I tried was to align the TimeSignature objects with the barlines
as break-align symbols:
\override TimeSignature #'break-align-symbol = #'staff-bar

But it doesn't seem to be working; moreover, when I try to apply it to
larger scores, it gives me the following error message:
"No spacing entry between TimeSignature and time-signature"

( I can send a larger example that produces the message, if necessary)

A solution would be to print the time signatures as Rehearsal Marks,
but I don't know how to do it nor if it's even possible.

But what isn't working here?

Thanks,
Valentin