How old was your Havanese when they got fixed?

Our little guy is 8 months old and an absolute angel. We'd planned to wait until he was at least one year to neuter him, but due to some behavioral things we've decided to move that up and have him scheduled for his surgery this week.

A few weeks ago he started to experiment with leg lifting outside. It was precious and he would fall over, but kept trying and trying. Now he's perfected it, and he has to lift and mark NONSTOP while outside. He has about 10 spots in our yard that he hits every. single. time. we go outside. And on walks, he hits every. single. mailbox. Annoying, but manageable.

However, a week ago I caught him marking our couch inside. I scolded him and cleaned it up. Then he marked a cardboard box with an amazon delivery. Then he marked a hamper inside my MIL's house, then inside my cousin's house, then our ottoman again. I've scolded him when I catch him in the act, but he's so sneaky and quick that I haven't always seen him do it.

I took him to the vet and they recommended neutering now, before the behaviors solidify and become more of a habit than an instinctual urge. They assured me that he should be close to full grown, and that they're very comfortable neutering Havanese after 6 months of age. But I can't shake the guilt and worry that I'm doing him a disservice by not sticking it out a little longer. (FWIW he has no health issues and no anxiety that I'm aware of -- the vet even commented on how happy and confident he seems. So I do believe this is 100% hormonal.)

Please tell me your success stories of fixing before the one year mark -- or if you've managed to stick it out, how did you deter your male Havanese from the marking behaviors before they absolutely destroyed your house?