Hi and welcome to GP!
Small breeds mature quite faster than the larger ones. He will probably slow down by 9 months, It's hard to say with mixed breeds cuz I have seen some pretty big purebred cockers. I hope the "breeder" you got him from was a good one and not a BYB who is doing it for money and nothing else. There are plenty of poo and oodle mixes in the shelters because these days they seem to be crossing everything with them, go through some of our older threads and read some they are quite interesting. Good luck! and I hope you enjoy GP!
