thanks for a reminder, I was going to replace mine and forgot
Soft side is intended to get good grip on velcro IMO. The pad is under heavy impact of balls rotating at high speed, so coarse side up. Look at what the balls did to mine... Had it been soft side, I would have had to replace it in a month of use I suspect.
And since mine has been never changed before (I think) that's the way it came manufactured.
edit: and it turned out to be pretty straight-forward once you try it: there is no way you could make coarse side stick to velcro base