Undoubtedly, at least a 240...but that's still a little small, IMO...again, it's just my opinion, but those are all large fish. As I said before, if given proper habitat, they will reach those lengths.
Mysis is ok, for small fish but your guys are getting up there, in size and need some more substance, to their diet. Brine is basically useless and holds no nutritional value for those types of fish. Silversides are basically bones and water.
You'll need to get them over to a diet of krill, octopus, squid, chopped fish...no live feeders.
And lastly...fish will not stunt their growth. They will, as you said, continue to grow and get stressed and die in an undersized tank.