Some help regarding Unicorns and Dart 15s please..

My son turned 14 last week, but despite his young age he stands at 6'1" and weighs in at 78Kg (and rising!). He's always been big for his age and consequently his sailing peers have always been at least 2 years older than him. His stated ambition is to represent GBR at the Olympics, probably in a Finn.

Since entering competitive sailing about 5 years ago he has done the Squad "thing", with Topper Zone Squad then on to 4.7 Nat Squad. Last summer he moved into the Radial and did superbly, getting in to the Gold Fleet at the Nationals (he's still only 13 at this point remember!). He also this year had the opportunity to sail a Spitfire a couple of times and did suprisingly well at the Nats, a result that ended up with him being offered at Youth Squad place in that class. He turned this down in order to try and gain a place in the Radial Transition Squad, but was unfortunately unsuccessful in this.

One thing I have noticed with his sailing is that despite his excellent sailing skills and physical prowess, as a genuine youngster, he isn't yet equiped with the emotional maturity to deal with the pressure (when he feels he has something to lose, like the Squad selectors, as opposed to the Nationals when he could just go for it) and the enevitable mind-games in the Youth Sailing enviroment.

As an upshot of this, we've decided that his best way forward is to "escape" from Squad chasing and to get away from the Laser youth circuit in order to do something completely different on order to just have fun enjoying sailing for a year, before going back in renewed and refreshed to have a crack at it again (subject to his size still being appropriate for a Radial).

So.... back to the original question...

I've got a budget (ish!) to buy a boat each for the 2 of us, of £1K each. We're looking to club race at Farmoor, do the Open Circuit/Nationals, and some Open Handicap events, like the Weymouth do in the summer. I've got a bit of a short-list of classes, which all have their pro's and con's, so I'd like the esteemed panel's thoughts...

1. OK - I love them, good boat for budget but too similar to the Laser...

2. RS600 - Budget? Poor turnouts at Opens. Very physical for this old git.

3. Contender - Budget (for a half-decent one)?

4. Dart 15 - Great Class setup, competitive at this price?

5. Dart 18 - Sailed unarig, much class racing?

6. Unicorn - very fast and fun but class racing? Fragile?

Any comments on the above, or other ideas?

The original question was asked regarding the kind of boat I could get within budget, specifically with the OK, but is just as applicable to the contender and Unicorn.