The pilot was flying one of three similar aircraft in practice for a forthcoming aerobatic display. The three aircraft carried out a stream landing, with the pilot of the subject aircraft intending to land to the left of the centre of the strip. Shortly after a normal touchdown, the aircraft encountered a soft area of the strip and subsequently overturned, coming to rest 85 metres from the initial point of touchdown. The display team had had no prior indication of any soft areas on the strip surface.