Trying to set global staff size on the commandline using -e option

[James]

Hello,

Here is my simple example

--snip--
\version "2.16.0"

{ a b c d }
--snip--


My command I am trying to run is

lilypond -e '#(set-global-staff-size 32)' --pdf myfile.ly

I get no warnings or errors and the files compiles but the staff size
has not changed.

The Usage suggests

adding

#(use-modules (guile-user))

to the top of the .ly file but it doesn't make any difference either -
I get a warning

'Parsing...WARNING: #f: imported module (guile-user) overrides core
binding `%module-public-interface''

But the file compiles with no other warnings and no errors and still
looks like the default size.

Perhaps the syntax is incorrect?

Thanks for any help.

James