Agree with Mark. It's generally a non-issue but what you need to include in your request is a rough position and the altitude block you'll be using. Furthermore, be cooperative if they need that bit of airspace for something else (it's not controlled for nothing) and report when finished.
I regularly fly aerobatics in class E and although legally I'm not required to say anything, I treat the flight as a controlled flight. So I request permission to do aeros in their airspace, keep ATC updated on where and what I'm doing, work with them when they have IFR arrivals or departures through that airspace and so forth.
We have a very good understanding with ATC because of this and that regularly helps us in other places/situations.