Originally Posted by Duck

Yes I agree the client will have to be thin, I don't see a problem with that. Of course the physics could not be solely handled by the server over TCP since it would not be quick enough to run in 'real time' at the client end. But how it would work is, the server could keep track of the motion itself, and at the end of each players turn the server would check with the client that they both agree on the final position, just check for 'synchronisation errors' after each turn.