2 inches isnt that much of a difference in amazons, it might just well work!
I am in the process of taming our new addition Leroy before introducing him to Stitch, and while I want them together as soon as possible, I believe that you should let each step take its time.
We want Leroy to be able to step up, and preferably reasonably comfortable with hands before introducing them to each other. When doing that, I plan to take it really slowly, 2 separate cages in the same room to start with, followed by supervised playtime together, before eventually having them living in the same cage.
Still, even doing everything right and slowly is no warranty for it to work out, but you at least improve on the odds.
Our two guys are the same size, but different species all together, white fronted amazon and bronze winged pionus. From research and talking to a lot of people, these 2 species should mix well, but of course its down to the individuals! But I am gonna make damn sure to do my very best for it to work

!
This turned into a rather long post, but my point is, dont be sure it wont work. Look up the facts, research and talk with knowledgable people. It might work perfectly.
Take a look at things like, temprament, length, beak size, weight and see if they match. Also take into account that amazon are known to mix well together!