I've used the bedrock ceiling trick in my single player world. I believe Xisuma showed how to set it up early in season v, it's just finding that perfect bedrock spot that's the issue. My single player world is the season v seed, so I was able to just go to his same cords and locate it. That's why I was asking if their spawn explosion and attacks destroyed claimed blocks or not so I could build a containment building in the overworld to contain the fight. If, as you said, netherrack doesn't break when it's claimed, I think my idea would work too, although suffocating it in the roof might be safer still.