Hi Richard,
Another option to consider, though it certainly isn’t free. Bring your movie to a post/finishing house that can do a hardware down-conversion for you. Though you will, of course, pay a fee, you can end up with two things. First, the digi-beta master necessary for submission to many festivals/broadcast. Second, have them create an 8-bit uncompressed anamorphic file for you, which you can compress to mpeg2. This way, you won’t be paying the enormous cost of professional authoring, but the hardware downconversion will make the difference in aliasing/edging that you are noticing.
If you need a hand with specific machinery to request or houses which can do the conversion, let me know.
-joe