Bulkhead heights

I am struggling to get the correct bulkhead heights above the datum line in the jig. I am confident the jig measurements are all correct. The real big problem is F404 (spar box) which seems about 3/8 too low. F407, 408 seem about the same too high. These errors will throw out the rear spar location. I don't see how F404 can be too low, given the way it goes together......
I could enlarge the notches for the longeron in the other bulkheads so they sit lower but am reluctant to cut anything until I understand how the problems have arisen......

Any thoughts guys?

Thanks

Mine worked out well in the jig but were out 1/4"-3/8" when upright. I finally checked the overall bulkhead dimensions compared to the drawings and discovered none of them were the correct dimension from the factory. Check the overall dimensions of the bulkheads. You can more easily adjust the top than the canoe dimensions, so make them right in the jig.