Tank mates?

I have been raising up some juveniles to go in with my adults, an I'm really nervous about the introduction process. I feel the little ones are edging on adulthood- all a solid 8" long, their growth rate has slowed considerably, and one is clearly identifiable as male. The issue is, the adult male I would like to put them with is 10.5" long. I'm really hesitant to put them in together with such a size difference, and I'm looking for others with experience. I have done introductions before, but only with babies of equal size. The youngsters are definitely getting cramped in the tank they have now, so I'm feeling it's time to either introduce them or bite the bullet and buy another 40 gal to grow the out a bit more. How do I know when the time is right for introductions? Any advice would be appreciated. Thanks guys!

In my experience they should be fine with the larger adults. Before you introduce them just make sure everyone is well fed. Once they've checked each other out and maybe nosed each other about they should settle down and get back to normal pretty quickly.
All axolotls are different, so obviously keep an eye out for the first few hours of introducing them, but I've kept them together in the past with much bigger size differences without any issues at all.

I find adults are generally more tolerant of newcomers and smallers axies, juvies tend to get nippy with other juvies that are a little smaller.

So as long as your juvies are more or less the same size you should be fine.

Thanks guys! I thought they would be fine, my male is pretty low key, but I tend to be a bit of a worrier.