I too have trouble fmq w/ Essential Thread by Connecting Threads on my Viking Sapphire 875 Q. I get the globs of thread underneath, so much so that the machine will jam or break the thread. I have been using Bottom Line in the bobbin, so maybe those two together just don't work. I'm unable to adjust my tension any higher than 9.5 on top and it still doesn't work. Perhaps I should try have the same thread in top and bobbin. I also use a Topstitch 90/14 since this 50 wt. thread does seem to be thicker than other 50 wt. threads. Well, I guess I have one more thing to try. I'd hate to not be able to use all the beautiful colors of that thread that I have.