Hi,
I've started IMAC this year and am having a great time. To answer your questions.
1) IMAC this year is around 8 events spread all over the country.
2) IMAC is similar all over the world (as i understand) BUT we use the European rules which means the aircraft need to be within the 10% of the scale outline of the fullsize.

What we do is fly scale models of aerobatic aircraft past and present in a preset schedule. We are also given a schedule on the day to fly as well as, which adds to the fun!
The freestyle is run as a seperate competition over here, so its completly optional!

The best way to see what we do is get in touch with the IMAC secretary (Phill Goddard) and get to an event, you'll soon see its lots of fun, relaxed and that were a friendly & helpfull bunch of people.
Hope to see you at some events.
Rich