It's probably a little of everything (rice, steaming, resting, tray, temperature (93-95 F), but this is by far the best looking Koji I've produced yet, and the best behaving. No wide temperature swings into the 100's.
A toji I was speaking with suggested a cedar tray, lined with mesh (soaked in water one hour), for the 2nd half of the incubation. Basically as a way to reduce the humidity content gradually. Have to say it worked great.
I was a little nervous about it going to spore and pulled it at about 42 hours. Looks like I had nothing at all to worry about. I have a small amount left in the incubator to spore and at 72 hours it is even more heavily covered with mycelium but no sign of sporing. Still bring white.