I don't know if anyone else knew this, but when you punch-
in in Vegas with preroll, it actually records "underneath" 
the preroll. That means if someone starts early, you can 
actually "uncover" what they did by dragging the new event 
over and dragging the left edge of the event to the left to 
uncover the preroll portion. This is really helpful for all 
those times you think you may not have caught an early 
entrance. It's not helpful if you're trying to save disk 
space, however :)
I thought this might be helpful info to some...
Charles.
CDM Sound Studios, Inc.
NYC