So I picked up a wicked series slate and really like it, however the sweet spot on the back does absolutely nothing. I mean no sound what so ever. I'm assuming it needs to be sanded and prepped since it is incredibly slick and makes no noise when touched with the striker. Its such a small spot I'm unsure of what sandpaper I should use. Anyone else ran into this? I figured it would be at least prepped a little from the factory for use.