Like canoepam I do not piece with poly because I have melted it with my hot iron.
I just tried bottom line for quilting and loved how much of it wound on the bobbin. I adjusted the tension at the bobbin as well as top thread to matched it with king tut, masterpiece and sulky 30 cotton.
I do wonder if the 60 weight was a poor choice for quilting because it does not seem as strong but time will tell.