Increasing space between notes?

[Graham King]

The three bars in the example below illustrate a problem in the middle
of a piece I'm transcribing.  The composer has written sfz followed by a
diminuendo onto the following note, but lilypond does not make enough
horizontal space for the ">" diminuendo.

Bar 1 illustrates that problem.  Bar 2 illustrates my work-round to
force enough space for the dim.  Unfortunately, the work-round does not
solve a similar problem (bar 3) where the diminuendo ends on a rest
rather than a note.

I've tried too many different things to remember, let alone describe
here.  Please help!

-- Graham

\version "2.4.1"

\paper {
        raggedright = ##t
}

\context Staff {
        \time 4/4
        % This bar gives "warning: decrescendo too small" :
        a'2->\sfz\> g'4--\p f'--

        % The next bar is kludged to make enough space for the dim.:
        << {a'2->\sfz\> g'4--\p f'--}\\{\hideNotes g'4 g'4 g'2}>>

        % But the kludge does not work for this bar:
        a'2->\sfz\> r2\p 
}