Question: When to introduce axolotls together?

Hello! I've only ever owned 1 axolotl, and he is reaching his third year now. I recently decided to get another axolotl and hoped to introduce them to each other in the future to keep one another company
The problem is, I'm not sure how big a difference in size is acceptable for them. One is 11.5 inches, and the other is 7.5 inches. There doesn't seem to be a set standard to measure... I searched the forum and had seen 3 different recurring rules:

Juvenile must be A) 2/3 of size B) 3/4 of size C) minimum of 2 inches in size difference

Following these rules, we get very different sizes... the younger must be A) 7.6 inches B) 8.6 inches or C) 9.5 inches before housing with my older axie.

So which answer is correct? I also realize it depends on other factors, such as temperament. I am not so much worried about the older one bothering the other...he is very slow and gentle, and takes his time coming over to eat his earthworms. However, the younger one is very snappy-- I'll just be walking past his tank and he runs up to the glass and snaps at the water. When I feed him (1 whole earthworm every day to every other day-- he's gotten so fat...) he wildly bites at it, sometimes missing because of inaccuracy.
Even if he is big enough at A) 7.6 inches, should I wait for him to grow out of his nippy habit? Or would introducing them via tank divider be fine? I would hate to endanger the younger due to size difference... or risk the older one's gills/ extremities being nipped off.
Thanks in advance-- any advice/ experiences would be greatly appreciated!

Hi , im the same position I have one about 9inches older than other but alot bigger thickness wise and other is 7inches and only 5mths . The 5mths is a wild one and have heard they are a bit more aggressive ? Bigger one is Albino and very chilled.
Wild one had no ext gills when I saved him from attack from another wild juvenile ( plus other bad conditions etc ) Albino has long wonderful ext gills which Im thinking may get eaten by little one or my big albino may just eat the other ?
Have a divider in tank at the mo to see how they react through glass just started today.
Albino wandering around happy ,the Wild one was staring through glass for first couple of hr's , now has settled since being fed.

The divider I've put in to try and introduce them but think there size may be just too much ?