A few weeks ago I made a pair of boxer shorts for Calvin, using the First Choice Boxers pattern from Timberlane Press. I compared the pattern to a RTW pair he has, and decided on tracing off a size 2 (yes, a size 2 for an almost 7 year old!). They fit well, but before I made up a bunch (because he'd rather go commando than wear regular underwear, and we can't find RTW ones small enough), I wanted to try them again in a size 4. I figured if they were just a titch bigger, he'd be able to wear them longer.
Saturday afternoon I traced off the size 4 and made a pair up. I also increased the waist elastic 1" from the previous pair (but still quite a bit smaller than called for in the pattern). They fit great! He loves them, and now I need to get a production line set up and start a Boxer Bonanza. I'll do some in cotton, some in flannel, maybe some in knit, and he's requested a silk pair as well. HA! A six-year-old with silk boxers! :)