5 might be a bit too muh IMO
, try 3 at first and unless you see some fighting leave it at that. Pajamas seem like small fish but when they grow they're pretty hefty.
If you really want a tang I say go 6ft, 90Gs are just tall 4 footers, I'm personally not a fan of tall tanks though. And this would be something I would play it safe on, I usually would push the boundaries but not on this
Edit: I see you pretty much changed your mind, maybe try no centerpiece, just several single interesting fish. This would be a good tank for a flasher wrasse