What type of kiln do you have? Are the elements in the top or the sides. If they are in the sides the heat can pull your glass pieces unevenly. Tack fusing is something you will have to experiment with your particular kiln. I find that lower temps with a longer soak work best. Also you are experiencing the different flow/melting temps of each type of glass. Black 100 vs Stiff Black 101 this is all part of the learning process. I have had dichroic pieces leap from one piece of glass to another. All is not lost. You can always fuse up to approximately 3 times sometimes more depending on the heat as eventually the compatibilities of different glasses will change. I have not had it happen to me yet.