Thanks. Nuts - board alone is 160cm never mind packaging or the board bag. Me thinks this will not be as easy as I had anticipated!
Limit might be 165cm. Double check with the web-site (or you might need a Japanese speaker to call up takkyubin).
But it is probably going to be tight - my pow board is 163 and with the bag (and some cardboard taped to it - takkyubin only accepts 'packages, not bags/suitcases for international shipping...) it was a few cm too long.