I started printing with glass on my Dreamer a few days ago, and I'm having far, far more success with my prints not slipping than I did before. I'm actually attaching the glass via hair spray -- spray the Kapton tape, set the glass on it, then spray the glass. Someone on Reddit had made that suggestion, and it seems to be working just great. Same person also claimed that the glass will come off easily when you want to remove it, but I haven't tested that claim yet.