The two things I have found are necessary are Corel Draw and a healthy amount of cursing, as it never seems to work right 1st (or second, or third!) time.
I tried Inkscape but found it to be unreliable.
If you can get what you want from the scale.html lino that Weiss posted, that's by far the easiect option. There's also a small Java app which does something similar on the front panel express website which I've used with success in the past.