Eric,
The gusset sits on the rib face since the rib is 3/4" wide and is half lapped to the 1" rib riser. I half lapped on the 1" rib riser so the gusset would be level across the face. If you look at the midships section on the resource the Ribs are 3/4" wide by 1" deep, the Rib Risers are...