I know what ya mean, all my panels fit so well when the fitting and blocking is done that when I put a machinist straight edge from panel to panel you can't see a crack of light-I'd like to have it reassemble to the same specs but coating thicknesses change everything. I have had some success by applying a few layers of masking tape between decklids and hinges to simulate coating thicknesses during blocking and this is a critical area where there isn't supposed to be any shims. I do keep primer thickness to a minimum in these areas but sealer, three coats of base, three coats of clear X2 surfaces adds up to enough to throw it off. I might have to guage the paint film thicknesses and come up with a shim close to install during fitting that I can pull out during final assembly on future projects.