Thank you to Phil and Thomas for a quick response! I think Phil's response was "tongue-in-cheek", but I'm not sure! :-) At any rate the result looks like my first example, so it wasn't an improvement. Thomas's suggestion works great and I hope I've learned a little more about tweaking as a result.
Can either of you suggest a good way to improve my knowledge of Scheme? (I know almost nothing: almost everything I know about coding I've learned through engraving music with LilyPond --- which I love.)
Thanks again, you guys are great! Someday I hope to join the bug squad again!
Mark