Mostert tops opening Perth practice, Heimgartner fourth

Chaz Mostert topped this weekend’s Perth SuperSprint opening practice, which was interrupted by two red flags at Wanneroo Raceway. Mostert’s 55.0930-second flyer came early in the 60-minute session, moments before the first stoppage came when Thomas Randle crawled to a stop on the pit straight with a prop shaft failure. Matt Stone Racing’s Nick Percat …