I have just been getting into IMAC in the NW region - a few contests yr before last and about 8 last year. My impression re mini-MAC is this.

1) In addition to 8 plus contests, I would like to attend more contests without having to drive 300+ miles and therefore would welcome another competition format.
2) Size of the closest airfield, which is in an in-town park, is a huge issue. 50 cc engines are probably the max tolerable. The next field (for big stuff) is 45 minutes away for me.
3) Many of the basic and sportsman pilots in this region do have 50cc and smaller planes which we use for practice at size restricted airfields.
4) A mini-IMAC at the park airfield would be very welcome, and as there are aprox 300 members, it would likely encourage some now on the fence to start competition.
5) In our region we are starting to see 35% planes in basic and 40% planes in sportsman. There is a big difference in how these planes fly and glow sized planes. This is fine with me, but it does discourage a lot of folks from going to any IMAC contest with a small plane.
6) It seems to me that where the real airplane cost begins to hurt is when you pass the single cyl to twin, one servo per control surface breakpoint.
7) In addition to cost, time is a factor. Some pilots can not get the two days needed to fly a normal IMAC but are able to do a one day. Also field availability increases when a host club only has to dedicate one day and personel for support is more likely to be available. The small contest factor also works in favor of mini-IMAC because with a small number of pilots things go much more smoothly at any contest. There is less waiting around to fly and perhaps single instead of double flight lines all of which helps a novice feel less pressured.

My view is let's encourage any form of mini or "CLUB IMAC" to increase avalability of aerobatic competition and interest and support for it. With respect to IMAC as it is, I personally think the present rules are fine - it's not broke so don't mess with it.