As an engineer.. Seriously, how much stuff is there to "Review" if it's a 1 for 1 dimensional replacement of a current part, made of better materials, with a modern process that is less likely to have hidden defects. OH WAIT.. THE FAA IS INVOLVED.
An FAA certified "DER" Designted Engineering Representive charges as much as $500/hr and they can take as long as they deem neccessary to ensure the safety of the certificaton/modification. problem is, they apply the same standard to a new Cub or Stearman part as they do for the composite turbine passenger plane.