S2 7.9 Meter Class Association

is it ok to haul a 200 lb person up the mast ?

...board down, in the slip, on a light air day, with a safety line, no big deal.
...out on the water in waves or puffs, things get 'interesting' more quickly. Be sure to have somebody on another boat with a video cam when you attempt option #2.

Can you find a smart enough 90lb kid to do the job?

for a couple of quick fixes to the masthead, recover a lost halyard, etc, we have dropped the mast at the dock, fixed, and reraised. All within 30 minutes.

I have had my 190 lb behind up the mast at anchor and at the dock for various reasons.
There has been no obvious damage to the rig or deck.
I would only do this with a halyard that is in very good condition and with a proper knot tied (follow there figure eight or bowline with a stopper) rather than trusting a shackle.
It is probably a good idea to keep crew weight centered while your up there.

We've put a 180 lb person up to the masthead with no problem with the sails down.

well , I installed a flicker / spectra backstay rig before launching, using a batten that I thought was stiff enough, but not too stiff, rigged the whole thing up, pulled on some backstay to test it, and on the first try the batten snapped. so, it's up the mast I guess - I'm not to keen on dropping the mast on the water. hmmm.... I'll get out the video camera anyway!
my main concern was the side sway of the boat and where the point of going over is - the point of no return.

I'm 210 and I have been up - dockside - to replace a light bulb. I was winched up in a bo'sun's chair. If the standing rigging is tight, it should not be bad.