Joel,
Here is my experience. I have bred both forms at 3yrs of age and approximately 40" long. I do not recommend this as this species is easily stressed and reproduction is biologically speaking, a huge effort for a young animal. They can be harder to start and therefor smaller at a given age compared to some other Pituophis. If you can, it is in the snake's best interest if you wait until they are a bit larger and older.
I have brumated mine similar to other Pituophis with durations of 3-4 months and temps as low as the mid 40's, although they are typically in the mid to upper 50's during this time.
I think cluth size is quite variable ranging from 8 or 9, 12-15 being typical but I have routinely had clutches greater than 20......(I once had a jani lay 28 eggs and all but two were fertile)
hope this helps