Ken -

I've had to design around issues where the post above the tie beam is a lever arm, and the thrust from the rafter wants to shear the post off at the tie, as it is assumed the tie is doing its job and resisting the tension. This type of configuration can be tricky to get right - its a balance of having the tie close enough to the rafter, but still far enough to leave enough meat for joinery. I can post a sketch when I get back into the office as I can't seem to attach anything from my mobile.