Hey everybody, so I hAve been ordering my slate through an online dealer (don't want to burn anybody but they are reputable) and have noticed that most of the discs have been slightly cupped... if you put them on a flat surface they will rock back and forth... Instead of being flat | they are shaped like this ( Is that normal or should I try ordering from somebody else... Some of them look ridiculous when I try to glue the surface in. Thanks in advance