In reading all the post to this question, I have one issue that hasn't been mentioned, but adds some degree of merit to the mini-mac in my opinion.....

Field Size!!!!

There are a great number of good flying fields where an aerobatic contest could be held, but not with a 40% model.....they just eat up too much air space too fast.

There has to be a number of clubs that have IMAC members that would love to host a contest at their field, but their field doesn't present them the opportunity for a 30% to 40% model, but could handle a 40 / 60 size model based contest fairly easily.

I honestly believe there is a place for 40 / 60 size aerobatic contests, where you can get a taste of the requirements to fly controlled aerobatics and have fun as well before moving up to basic and the "Big Boys".

Additionally I don't think coming up with a set of rules would be a problem. Its suppose to be fun, so make the rules a little more open and relaxed.

I think the the hardest part of this whole experence would be finding the right people with the extra time to organize this style of event.