Pilot is climbing at the same time as operating the hopper dump facility. Not a problem for a 'sound' machine, but these aircraft have been doing this for years when spraying, and there are numerous 'AD's' for struts, centre cluster. wing fittings, that need to be kept up. In actual fact the 'dump' reduces the actual load instantly which could mean an increase in the climb rate. In normal spraying ops the load is gradually reduced over several runs although some 'spirited' turns are frequently seen between runs. The combination of a high lift wing. plenty of power, and the ability (if wished) to instantly reduce load could easily lead to an overstress situation, and the wings are load lifters but not for abrupt manoeuvres.