Drilled the top skin F-821PP to the longerons after I made the big cut required for the Fastback kit. Used a high speed cutoff wheel and then final trimmed with a file.
I back drilled the #30 holes that go through the engine mount brackets. This is a before pic.
All the holes lined up nicely. Make sure the fastback canopy rail is level. You can see in the following photo the proper arrangement. It does not follow the contour of the longeron and the top skin is cut level with the canopy rail.