I am ready to install the beam just aft of the forward bulkhead. The bulkhead is set at 48" and the beam is to go on at 60 3/8" from the steam ( most forward point). When I pull a string line from the stem to the top of the beam at center, the top of the bulkhead is down about 1". As best I can tell from the pictures the bulkhead should be on the same plane as the beam at top center. What gives?