I very rarely have to slow my machine down. Before I load a design onto my machine I pull it into my software program and add jump stitches, and reduce the density and any underlying stitches that aren't needed. I do slow it down when doing FSL or a really dense design if I'm having problems; which is rare. I have the Viking Diamond Deluxe and had the Ruby before that and I've rarely had any thread breakage or tension problems. I've never changed my tension settings because my machines take care of that for me.