You're going to have some serious port noise if you approach anything near xmax. Which is about 1kwatt. You could underpower it, but that seems pointless. Consider 4x3" ports that are 60cm long for a 20hz tune, or some a way to get that port working. That's still not really ideal either. I'd be thinking 4" ports. That's where slot ports are nice, you can extend them along the side of the box and get lots of mouth area. You might need elbows in your PVC.