IIRC the Jigsaw trials hoist installation was far more sophisticated and provided fixed speed control from the pilot's collective for just such an eventuality. For the trials the aircraft (JSAR) carried the Eurocopter mechanical installation and a Bristow developed control system based on the S61N installation used successfully on the MCA contract. Not sure why this was not specified by BP as a requirement for the full contract, probably ECF did not want to pay Bristow?