Hi jordanal,
I had the same question so searched the forum and found your post. The FSUIPC 3.98 User Guide page 28, para 8, says that there are two ways (manual and auto) to assign alphabetic IDs to control devices. It then describes the first method as preferable, which is to assign an alpha ID to a name in the JoyNames section, but it doesn't say specifically HOW to do it in that section, even though one could say that it is implied. Like you, I'd rather use the preferred method.
So... you manually added three lines to FSUIPC.ini in the JoyNames section (a good guess, but one shouldn't have to guess).
You seem to have also manually edited the Axes section so the IDs match the JoyNames section. Nothing is said about that in the U/G and para 5 on page 28 of the U/G gave me the impression that once you changed the JoyNames section, the Axes section would be updated automagically. I'll try it.
Thanks for raising the question. I didn't have to. It's unfortunate that Pete told you that you didn't know what you were doing and that you should just try it and see. I think it was a legitimate question. And in suggesting that you could have used the autoassignletters method he didn't seem to realize that if you wanted to do that you would have done so and your post would not have been necessary in the first place.
G