BigMike,
You might need to check that the B427 is certificated in Category A; to my knowledge it is
not - hence one of the imperatives for the work on the B429.
Certification in Category A in accordance with Appendix C of FAR/JAR 27 goes well beyond the requirement for performance data; this was exhaustively discussed in a recent thread that can be found
here. Performance data in the RFM is not evidence of certification in Category A as Nick Lappos pointed out in the same thread.
You will also be aware that operations in PC1 or PC2 in compliance with JAR-OPS 3 requires certification in Category A. As the B427 was certificated after the introduction of Appendix C to FAR 27, it cannot take advantage of the alleviation contained in IEM OPS 3.480(a)(1) and (a)(2) which was introduced to cover helicopters certificated before the advent of that Appendix.
Jim