Not 'onerous' at all. There have been a number of fatal crashes in the last 10 years that a definitive cause has never been found, as in the Cessna accident. The TSB had made previous recommendations to TCA to require Light Weight FDRs on smaller aircraft. The TSB has recommended it again. And BTW..this recommendation is not for just commercial aircraft, but private operations who have aircraft that fit inside the recommendations. It is a major step in the right direction of safety, but ultimately we have to see where TC is on this issue and if they stand up and make the changes to the CARs.