That is the size of our travel carrier for our sun and he does fine in it. don't like to leave him in there more than 3-4 hours, because he cant stretch his wings very easily, but most of the time we take him, we are around and he can be let out to play. Take perches that you can attach to the outside of the cage too (and a blanket for the top). And the playstand is a great idea too.
Here was is our setup (this was over Christmas for a month!):
