That's a gorgeous bubble, Fliger.
I've had around 6" sweepers off my bubble a few years ago ... they can be hugely aggressive, difficult to find space for. Mine still show sweepers time to time, currently when I move Rics near them/upstream it seems to go from no/tiny sweepers to 1" in short order. Water changes + move a few corals away ... they drop down and slowly get back to 1/4".
IMO/IME, bubbles, maybe partly due to their large expansion/contraction seem to `smell' other corals pretty well, and often respond to other LPS/rics/?? by developing very large stingers/sweepers.
In some cases, this might `work'. IME, there will be many a case where this won't work ... this hobby is full of so much we don't understand that what seems to affect mine may/may-not have anything to do with your situation [as you know

]
IMO, experiment with other corals around it [do concurrent water changes as both can reduce sweeper size - at least over time] ... maybe you just have an aggressive one, that always will have long sweepers. IMO I appear to be lucky, as mine [while not that awesome color] seems to be much more peaceable with the open brain in another tank, acans/rics 6"+ away.
Though perhaps there's one coral in the tank that triggers it ... or not. Hard to know really.
That's a heap of opinion about sweepers, take as you will, pick it apart, throw out your ideas. The more folks experiences I hear, the more I reconsider my own.