I have yet to find a thread my S16 won't handle. I have used polyester invisible, metallics, pretty much all the popular quilting threads (including Magnifico, SoFine, and King Tut) plus a number of polyester embroidery threads. Look up Rhonda Bracey's blog post about tensions and look at the HandiQuilter site for their video about tensions. Basically you adjust bobbin tension first then the top. And yes, you can adjust the bobbin tension! Remember that on long arm type machines like the S16 you have to change the top tension knob a full turn before any real change is seen; be bold! Enjoy your class.
Pam