After trying to figure out how to make the chainmail show underneath I ended up just sewing the strips inside the bottom of the leather tunic. I had just one long rectangle left over from a butcher's glove my son gave me a few years ago, and I split it lengthwise unevenly - on purpose - so it wouldn't be all straight and neat. That took three days to cut - one tiny ring at a time.
Now the only thing left to make is a harness so he can carry his broadsword on his back.