Metric System for Old School D&D: Weight and Encumbrance

Call me biased (having grown up in Japan) or New School, or whatever, but I'm a big proponent of the Metric System. I'm also a big fan of how RPGs make math meaningful for kids and want to sponsor an RPG club when I'm a teacher. I think the US will, at some point in my lifetime, switch over to the Metric System, so I figure I should have a good, solid, playtested way to use the Metric System in the games I'm going to teach them.  I, and my similarly biased (having also grown up in Japan) roommate from college days, have been working on how to do this, off and on, for maybe six months now. I'm going to start posting bits and pieces of it here, as that was one of the reasons I started this blog in the first place.

I figure we'll start with the encumbrance system.

The base unit for determining encumbrance is the kilogram (1000 grams). Some items will weight less than a kilogram, but nothing will weigh less than .1 kg (one hectogram). Creating a long, very complete item list with weights and prices is probably going to be what takes up the most of the time we put into this system.
We've started that process, but have certainly not finished it.

The encumbrance system is based around the idea of a Base Movement Rate, or BMR. Each character, based on encumbrance, is assigned a BMR of between 1 and 4 (monsters, exotic or magically aided characters might have a higher BMR) which can then be multiplied to determine how far a character can move in a certain amount of time in certain situations. I stole the BMR from Swords and Wizardry and divided it by three, since it was in feet and we're using meters for this system.

To determine what a character's BMR is, tally up the weight of what your character is carrying. Kilograms, by the way, hit a midpoint of granularity between the currently fashionable stones and the old-fashioned pounds. I actually tried using stones, but the player who is working on this with me revolted over them being too big, as far as units go, hence us working on this system to replace it.

Once you've determined the number of kilograms your character is carrying, compare that to your character's strength score. Consult the following:

Equal to or less than STR Score:   4

Twice STR score or less:               3

Three times STR score or less:     2

4 times STR score or less:            1

No character can carry more than 4 times his/her STR score in kilograms.

It turns out that this makes for a simple, elegant and reasonably realistic system. A kilogram is about 2.2 pounds, so an average strength character (STR 10) can carry about 22 pounds without being encumbered and can carry no more than around 88 pounds. A character with STR 18 can carry almost 40 pounds (39.6, to be exact) without being encumbered and can carry up to 158.4 pounds.

Thoughts?