Noel,
Ya gotta talk to me about the technique for now, and sans anything written, it is easier to show & explain than describe it in written form here. Suffice to say that a transfer tool is made with precision drill bushings, potted in with tooling stone (or similar, like dental plaster), so as to pick up existing hole position and angularity of the eight 1/4 inch holes common to the c-section fitting area and the composite spar buildup.
This approach works well, and is superior to any machine shop approach - we use such "on-the-spot" transfer tooling techniques when necessary for airframe mods or repairs on the big birds. Work severy time, and is cheap. See this forum for a notation from Drew Swenson on how he did his engine mount extrusion replacements this way (topic was "Major Alterations" or, "Canard Vortex generators").
Happy to show you the basics if you want.
Cheers,
