We see a fair number of completion inspections where I work at
Velocity. The inspector tells us the rules for data plates have
changed in the years since 9-11 and the FAA requires the inspectors to
be more strict. Old installations are OK. New inspections have the
data plate on the outside of the fuselage, pilot side, to the rear of
the entrance (canopy) and visible from the outside. Typically under
the wing as close to the door/canopy as practicable.