Font sizes change on change of font

[Paul Hodges]

I have been asked to change my serif font to Times New Roman.  I have 
done this, using:

   #(define fonts
     (set-global-fonts
      #:roman "Times New Roman"
      #:factor (/ staff-height pt 22)
     ))

as documented (the staff-height matches the global staff size).  But all 
my non-Emmentaler text (titles, tempo, text markup...) has now shrunk, 
and looks wrong alongside the notation and dynamics text.

Is there any way to enlarge the text globally?

Thanks,
Paul