I like to use Bottom Line by Superior for both top and bottom thread when FMQing on my Janome 6600 and my Handiquilter 16. My Janome seems to prefer poly thread as a rule, and I like not having the lint of cotton threads. The other big plus for me in using Bottom Line is that the thread doesn't stand out (60 weight) so my, ahem, irregularities don't show as much.