The choices are regen or preset. Regen has no meaning in a P2 environment, so all P2 recording is preset. Which is why there's no choice, there doesn't need to be a choice.
As for the FireStore -- I don't use it, I don't know, and I'd definitely defer to BenB -- that guy knows the FS-100 better than just about anyone.
Thanks Barry for the clarification. I was not able to get a running preset TC while using the FS-100 because the Panny doesn't start counting. The Free Run mode does work fine. Now if I have a tape in and the FS-100 as a backup unit, then the preset TC does start counting.
Ben, TC on the FS is set to EXT so whatever the camera sends out it should see.