As I understand it, when the cropduster was converted, probably the front hopper, pumps, fittings etc were taken out and the c of g moved way back. At that stage we are dealing with a new unknown a/c and have to do a weight an balance and add ballast where required. Now the a/c is given a new c of a. This was not done. The pilot would have applied the c of g tables in his manual thinking they still correctly applied to his a/c. The only way I can see the pilot responsible is if he was required to check that the a/c had a certificate of airworthyness after the modification. The air safety authority certainly didn't because at the time they didn't require it. That lack of legislation caused the accident. Then the head of air safety denied any fault because existing legislation did not reqire the a/c to be checked, and whose fault is that? Listening to him was like Richard Nixon explaining away watergate-