Brad,
I've seen pictures of some old frames in Germany that were 4 and 5 stories tall that were built with single story posts. I don't know how they were joined. I would guess just mortise and tenons.
But with green wood you have to watch out for the cumulative shrinkage of all the plates/sills. If you have a post going up to a 10" plate and another on that going up to a 10" plate and a third going up to a 10" plate, you have 30" of wood that will shrink a lot -- maybe 2" (I don't have my calculator and formulas in front of me).
that really gets to be a problem when you have continuous wall posts and an interrupted ridge post. When the beam that interrupts the ridge post shrinks, the ridge drops.
gh
