I'm a longarmer and this is just the nature of the beast.Maybe you could use "So Fine" or "Bottom Line"in the bobbin.These are bobbin threds that I have been useing for quite sometime.But dots on the back are virtually impossible to avoid.In a perfect world the threads would meet in the middle of the quilt sandwich and be perfactely[?] balanced.But no matter what the books tell you,that isn't possible.Are you using a domestic machine to quilt this,or do you have a mid arm or longarm machine?