Dan,

I've done what Jim mentions, with some structural screws thrown in there. If the enclosure system allows it, I've put strapping on the outside of the post that catches the flooring. With a conventionally framed wall around the frame, I've put blocking at that level. That nailer is not really taking that much weight (depending on the joist locations), it's really just to keep the ends of the flooring from flapping around.

On a separate note, I'm a big fan of Tim's idea of putting the tie beams at different heights, and using soffit tenons on one side.

Brad