Don't get rid of them yet.
Wait until SS6. Maybe, just maybe, we might get our U-flak guns back. On the other hand, I still have my U-flak gunners (L112). I'm now using one of them on my SS5 (in place of my Chf Seaman) because my SD is already above 800. I've learned how to dial in range and have hit some planes with the pop gun (34 degrees) too. I've dropped CVs without wasting another torp, polished off a depth-charge-dropping FF after I surfaced. They'll put a hurt on a FF, pretty harmless to anything else. But you can dial in range at 45 degrees and torment CVs with HH outside their range, while you recharge and refill air. In reality, they're only good for sinking a fishing boat. Not too many of them in Navyfield.
Also, you can super skeleton the gunner and lard up with armor and keep your speed.
Start using them.
I'd certainly trade a support slot for the U-flak guns back.