Tom, I breed aldabra tortoises and use vermiculite at 86 degrees and 80% humitity. I am not sure what type of incubator, however tortoise eggs need to be motionless. Mine take about 105 days before hatching starts.
If you want any further information or I can forward pictures of the eggs in vermiculite in a incubator set up for you, just e-mail me at ALDABRAMANGREG@HOTMAIL.COM. Good luck, Greg.