Generally, unless it is important, we don't cover that kind of thing. No one pays attention to carrying capacity. But we do have a ruling, based on a base kilogram amount with a bonus based on the strength stat. Oh!
That's another thing. Most stats are single-digit numbers. Instead of making 10 the 0-mark, 0 is. Negative numbers are allowed. Simply add the stat as a modifier. So, a strength of 3 is +3. Stats can also be reliably raised over time at a much more frequent amount. 5 is pretty much the highest a starting character will have, while 0 is probably the lowest (you can get lower, but that's traits).