My MacBook Pro is virtually idling at 57C. G5s run hotter than Core chips. I wouldn't worry. But if you really want get the fans up anyway, pull the baffler out. You should hear the fans ramp up shortly after you pull it. The metal tape on the right hand tab at the bottom means the G5 can sense when it is removed. Removing it screws up the airflow zones in the case and the unit defaults to high fan speeds.