So hybrids aside since that’s not really qhat the op was asking about and I’m not sure where they came up, I recently acquired some bull snakes for their size potential alone, let me explain. I searched for a breeder who was consistently producing excessively large offspring from exceptionally large parents and grandparents. The breeder i found told me that the way he has been able to consistently pick out and hold back babies that will get the largest is to wait for their first shed and count the belly scales. When you know the belly scale counts and can pick out those with the highest counts you have the best chance of bigger snakes. Now getting a corn snake breeder to count belly scales for you for a potential deal may be difficult but thats my .02 on it.
I’ll post some updated pics if anyone would like once I’m not sick and I feel comfortable handling the animals again.