If 1 6" tang in a 120 is bad, 4 in a 55(same length, not as wide or tall as you know) can only be worse. It's not like they stay at 2". Short term, sure it works. In a year, prolly not.
Please tell me why? If a 4' tank is too small for 4 2" tangs then a 8' tank is too small for 4 4" or if a 55g is to small for 4 2" then a 220 gal is too small for 4 4" because you're right you shouldn't plan them staying at 4"
