Percy Attfield has used a MVVS 8,0/680 motor on a 5-cell Thunder Power lipo.........think its 2500 mAh. His Impact weighs around 1750 grams and flies well with a 13 x 6,5 XOAR pusher prop. It's a jewel of a motor with 16 poles as well. It does cost a lot more than E-max but still cheaper than Pletty's and a little less than AXI. I'm sure that the E-Max will work as well and if any magnets come loose just glue them back again. The flight performance will feel the same and that's what's nice about electric stunt. You do however, get what you pay for and the better quality motors come with all-round better workmanship. I used an E-max 2826 in my Newtron in this last world champs and I did have a couple of MVVS motors in my stock. It was easier to mount and I also felt that I wanted to offer a high performance setup to the guys locally to show that you don't have to mortgage your house to get a high performance power package. In the 40 plus degrees heat (Celsius) I did have a magnet come loose but did not even notice this during the flight. I found out later when I spun the prop by hand and it made a bit of noise. I glued it back with cyano and it's still going strong. If I were you and had a couple of E-Max 2832's lying around........I would use one in the Impact.
Keith R