They can be quite aggressive, but they definitely aren't the most aggressive Old World Rat.
My pair is pretty chilled as long as they don't see any sort of tool that you are going to use on them (snake hook, camera, etc). Another thing about their aggression, it's usually a bluff. They will strike at you and hit you with their nose, but very rarely have I see one actually bite.
IMO, if you start calming them down at a young age, it should make them quite a bit more docile.
I have an adult pair as well. The female is pushing 8' and less than three years old. the male is pushing 9' and less than two years old. They are still growing in length and weight.
They are also great breeders! I didn't even mean to breed my pair and my female ended up laying 8 eggs for her first clutch. I was cooling them at the time (to possibly breed), found out we were moving and changed my mind. I split them up after I removed them from the cooling tub, which I had only started cooling them. They were together less than a week.
Blue Beauties are semi-arboreal, so they need a little bit of room to crawl around on branches, etc.
Female
Male (in shed)