If he's kiting in Perth (typical 20-25kn seabreeze conditions) then a 165cm twintip may be too big after the intial stages of learning. No problems if he's happy to use it in lighter conditions (a bigger, gruntier kite is far better though when you want raw power) or sell it, however if he only wants 1 board to last him a few years i'd look at a twin tip between 145-150 with. Varies on the board style and kite of course.
Even this year after putting on more weight

, i can't see myself ever wanting to go bigger than 145/150 for a TT.