The original system has been overhauled, in part due to playing around with the encumbrance system (which I'll post in another thread). I added a "no encumbrance" category, which better tied in to the various running speeds, then linked the different load and armor categories (none, light, medium, heavy) to the various movement rates (x5, x4, x3, x3, respectively). What we end up with is a fairly elegant system that still allows for realism. Not that anyone pays much attention to encumbrance anyway...
I've also added in mounted movement, which also ties into the encumbrance rules. Since it's greatly expanded (just over 3 pages now), I've uploaded it as a word doc. As always, comments/criticism are welcome.