Introducing a lone male

Question
My big buck (about 11 months or so) has been a lone rat for at least 3 months. I adopted him from my biology teacher who had received from a fellow class mate that could no longer keep him. A month ago I bought another rat as a companion for him. It's been a few weeks since the mandated month quarantine and I've done a few introductions. The first was fine for a couple of minutes but then Napoleon started becoming extremely aggressive towards the new guy. Well, I'm a new rat owner so it seems extremely aggressive to me. The little boy started doing scaredy poo and Napoleon was crowding him against the side of the bath tub and chasing him. It wasn't until the little one squeaked that I had had enough and separated them.
Since then, I moved the cages next to each other. The first week or so, Napoleon would puff and hiss through the bars and chew on the cage to try and get next door. He's settled down since then and only occasionally starts hissing and puffing. However, he will bite anyone that smells like Sholto (the new guy). For awhile I used hand sanitizer between handling each rat but he needs to get over it. For other introductions, every thing's fine until Napoleon takes extreme interest in Sholto and then things go back to the first meeting.
I've considered neutering, but I'd rather not put him through that stress if we can work through it. Does anyone have any suggestions???

Answer
I'd have Napoleon neutered and try again. The thing is an OLDER buck like that has his own way of doing things and his own definitive pecking order which includes just HIM right now. Neuter him, sanitize and rearrange the cage, and after Napoleon has recovered, try putting Sholto back in there. And remember that this time, no blood, no foul. If he isn't physically hurting Sholto, trying to physically hurt him (which means severe biting, not just standing over him puffed up), leave them alone. And if a fight breaks out, protect your fingers! A rat bite HURTS!