Flanker, anywhere in the backs. 5-10 isn't tall for rugby. He's too small for the front five or no 8.
Scrum half or hooker , hooker needs too be rock solid but a scrum half needs too be quick and have a good pass (:
Your son could go on the wing or Fullback
Wing. He seems around the perfect size for wing. however, Starting at 19 wont be easy. He will probably be a bit scared or intimidated....but once he realizes these big guys are actually softies, he will be able to run them over. I re started rugby at age 19, I had only player a dozen games at age 14. but I always watched rugby and new all the rules and stuff. Starting late at rugby...the coaches aren't going to hold your hand and welcome you with open arms to rugby....they are usually grumpy and will play guys who have experience. so I would say, tell your son to just go hard and impress at training. its completely within him to achieve success.
Maybe scrum-half or hooker? Don't know if he'd be better forward or back. If he has some pace maybe wing or even fullback.
I guess it's always difficult to judge without seeing them play, but judging off size alone, I would certainly looking towards the line! If he has pace then wing would be ideal, possibly Fly Half.
