we have just had barkley neutered at 12 months old and it still feels too early but unfortunately the decision was rather made for us by other circumstances. i had intended to wait until he was fully mature and at least 18 months old.
all i can say is that i feel, for barkley, 6 months would have been way too early. he has grown so much in character and build in the past 6 months, and his behaviour has never been a problem. i would leave it for as long as you can. luckily, our vet was very much of the 'if it aint broke, don't fix it' motto which helped a lot- particularly as it made us take his advice very seriously when he finally recommended that it really was best for barkley to do it now.
two weeks on, barkley is back to his old self, just minus a certain part of anatomy

, and i am realising and accepting that i will simply grow to love the dog that he becomes as a result, as i will never know how he would have been otherwise. it's a bit sad but ultimately i think it was the right decision for him.

edited to add to jaspersmum that it really is awful that your vets are pressurising you to have louie castrated.

i think i'd be looking for another surgery if at all possible, and definitely don't agree unless you feel it is right for him.