Is it wise to add cinnamon at this stage ??

[sssnake]

...clown that is!

I have a cinnamon clown in my 20 gal (which I am shutting down and giving to my bro).

I want to keep the clown and put him in my main tank 120g which presently is home to a false perc, two tangs and a coral beauty.

I know cinnamons are quite aggressive and territorial when they are the first in a tank. Seeing that he is not the first fish in my 120g will I be asking for trouble in putting him in there now?

Will he go at it with the false perc (nemo)?

[coral reefer]

I don't think you will have a problem especially with the size of your tank. As with any living thing you just never know, but on paper atleast you shouldn't have any problem.
Try adding the Cinnamon Clown at night after the lights have been of for some time to help the transition.
Good luck!