I'll use 60 wt thread in the Bobbin only when I quilt, not when I piece. When piecing I use the same thread in the bobbin that I used in the top.
I have to use the same machine from start to finish when I'm piecing otherwise the seam allowance may not be the same. I'll also use the same machine from start to finish while quilting. But it may not be the same machine I used to piece.