i have a designer 1...
the tension really shouldn't have much to do with which stitch you are using...stippling, straight stitching or any other decorative. the tension is based on the fabric itself and the thread being used. the easiest way to have your tension balanced is to use the same thread in the top and the bobbin. with my machine i have found if i am having tension problems it is either not threaded correctly (not pulled between the tension discs...only laying around them) or the bobbin area is full of lint and needs to be cleaned, or i've been going like crazy and haven't changed my needle in awhile. if you use the sewing assistant on the menu...set the machine to the fabric you are using (light/medium/heavy woven...or light/medium/heavy stretch...or leather...ect.) use the needle and foot recommended and your thread is equal the machine (should) adjust the tension on it's own. the self-adjusting feature has problems when the machine needs to be cleaned or re-threaded.