It can take extra time and practice to slump glass across a section's short span (2-5 inches across), especially if the sides are canted steeply. I think holding at process temperature for 10 minutes and then checking it every five or ten minutes would help you find the right cycle. Keep notes as you are keeping time. That way, when you DO find out how much time the slump will take under these circumstances (this particular mold in this particular kiln with this particular glass at this particular process temperature) you can program this slumping cycle in the future. In the future, even when you have the new successful cycle programmed, we recommend peeking at your project at the process soak temperature to make sure the piece slumped according to your expectations before continuing with the rest of the cycle.
Whether or not it will need to be at process temperature for an hour, I can't confirm.