On second reading of my last posting, and your subsequent reply, maybe I should not have said that moving the tie-beam down would increase the thrust. The amount of thrust is a given value, as determined by the roof slope, rafter length, roof area, presence of collar ties, etcetera ;however, the effect of the given amount of thrust at the tie beam location will change due to the increased length of post between the Tie Beam connection and the rafter foot. Sorry about that.
