[racket] Setting font for drawing to dc%

Hi all,

I was delighted to find awhile back that it's pretty easy to obtain a PDF of syntax-colored code that looks more or less like what I see in my DrRacket window, by drawing the text% to a PDF-dc%.  I am now using that in conjunction with the handin server to grade and mark up student work on my iPad (annotating the PDFs via GoodReader and emailing them straight back to students), and it works beautifully. (I am happy to share the code for this with anyone who is interested; email me if so.)

One glitch: I can't get Racket to give me a fixed-width font in the PDF.  I have tried inserting
  (send dc set-font (make-object font% 12 'modern))
where dc is my pdf-dc%, and alternately
  (send dc set-font (send the-font-list find-or-create-font 12 'modern 'normal 'normal))
but in both cases the generated PDF is still in a sans-serif non-fixed-width font.  It does not seem to matter whether I put the above lines before or after the
  (send dc start-doc "")
that begins the drawing process.

Interestingly, in a test I ran just now, if I generate a PDF by directly creating a racket:text% object, putting some Racket program text in it, and calling the same make-PDF function I use in the handin-server (calling set-font using the-font-list, as described above), it gives me fixed-width text as I'd expect.  That's regardless of whether I set the font before or after the start-doc command. (racket:text% is just a guess at the text% subclass that the handin server is providing, based on it being a representation of the Definitions window.)

Any ideas how to solve this, or further tests I could run to determine the cause?

Thanks for your consideration,
Jordan