I routinely use 50 wt 3 ply So Fine for all my piecing. For quilting, I use Bottom Line in prewounds (aka Super Bobs) and whatever I feel like on top. My machine takes whatever I throw at it - So Fine, King Tut, Superior and a Yenmet metallics, Floriani, Isacord, YLI, Guterman, Aurifil, etc. Learn to adjust your tension and your world expands.