The aerobatics are usually in one place, so it isn't too hard to work out where to avoid.
Exactly Carrot! Which is why it is so frustrating, not to say dangerous when someone does what was done at some of the competitions last year [and other years]. I think the worst one I saw last year was the idiot who did his own aerobatic display along the length of the runway at Elvington - not once, several times and without listening out on any frequency whatsoever.
He got his comeuppance when Church Fenton radar, which just happened to be operating that Saturday tracked him back home and the airfield management and/or CFI was informed of his exploits. The outcome could have been so different as at least one of the competitors was forced to take avoiding action.