I read again the 2nd, 3rd and 4th posting and need to add to it....Depending on waht level or aerobatics you are intending to accomplish.
Yes. the easiest is to fly above 1500 AGl in open airspace, away from any airway, population, etc.......HOWEVER...if you are intending to enter into competitions then I recommend a box near or preferably righ next to an airport for the reasons below:
1- Semi Controlled area. Many eyes in the ground looking for you if necessary while performing your flight. keeping you and others safe while practicing.
2- Issuing a NOTAM does not guarantee everyone will read it, however it does help. you have a preactice area and a legal safe radious around you.
3- Aerobatics are performed under high performance engine output and airframe stress...If any issues, I rather be right next to an airport for emergency on/off field landing and emergency response. Not the case in some open area!
4- Critiquing: Perfecting Aerobatics manuevers and/or practicing for competition is all about getting better and unfortunatelly you cant do it alone without others telling you what you are doing wrong. it might look great inside the aircraft and on video if you tape yourself, but without others telling you from the ground you are just a good airshow performer and not perfectionist.
5- having a legal APA will allow you to invite other IAC memebers or like minded people to come and fly together. You accomplish point #4 and also contribute to local economy and promote aerobatic flying in your area...
6- In "Competition" Primary and Sporstman are flown with a 1,500 agl floor. Intermetidate with a 1,200 AGL advance with a 800 agl and unlimited with a 328 ft agl floor... If you fly any of the first 3 categories, there is no reason while "practicing" for you to go below 1,500 ft AGL anyway....use that space between you and the ground as your safety area and venture into it as an ultimate resource. Stay above 1,500 ft agl and be happy, safe and keep insurance premiums low for our sport!
many more reasons....This is all I have time for it right now.....Others feel free to add to it!