Trying out the new position on a course on Saturday, luddite and I also found that unless the shooting area is totally horizontal, what starts out as a position where the knee is only contacting the edge of the bag, may end up by the time the shot is taken as the knee has slid onto the bag, and thus is contacting the shin. Even without any beans between two bits of bag material at that edge, any forward pressure results in the folded edge "rolling" forwards without the shooter being aware of it.
So it depends to a large degree on the interpretation, but if the strict interpretation of some being only "the knee" contacting the bag, that will an enforcement problem. As I alluded to before, even if the wording as per the minutes is taken "bulk of bag", it is too loose IMHO.
I personally found no anatomical stress issues as it's not a million miles away from my position, but the sliding forward/sideways as mentioned was a potential problem.