for any cinny x cinny pairing, you have a 50% chance of each egg being cinny, 25% chance super cinny, 25% chance normal

Snake growth is never a sure thing, so I'd say get a female already close to breeding weight(if you can find one) to be pretty guaranteed she would be of breeding weight. The smaller a snake you get, the less likely it will be the snake will be up to breeding weight next season.