Mixed games question

[Aragorn]

If you are running a mixed game, what do you require to be "in the game" when you switch from antes to blinds. Suppose you are playing stud and switch to holdem. The blinds are posted based on the dealer button.

If a player didn't play the last hand of stud, I would guess that the player is considered a "new player" and has to post an extra blind. Is one hand generally considered enough to qualify as "in the game"?

Any other thoughts on how that should work?

Thanks for any input.