Hi Kathy,
I am going to wait until I read other reviews on the new intensity series, because at the moment I still haven't had a go at IMAX 1 (which should be arriving in England for me, hopefully this weekend !). I don't have a medicine ball, as yet, but I do own a stability ball. I have seen in sports shops/wholesalers, that you can buy a plinth for your stability ball, so it is kept in place while you are working out on it. Might be worth looking in to ?
I think out of all of the new videos, I am most looking forward to IMAX 2, based on the fact that so many love IMAX 1 !
Anna