I don't do either. Like a lot of the posters above I do shorten my stitch length. Newer machines come preset with a larger stitch length than they used to. I.E.: The new (last 10-15 years) Berninas come with a preset stitch length of 2.5, I dial that back to a 2. I remember on my older Bernina (can't remember the model) 2 was the standard. I think that we forget sometimes that sewing machines are not built/set up for quilters, they are set up for sewers (garment/home dec). Try lowering your stich length and testing your tension (upper and lower) until you get a good stitch - just play for a little bit. If you take 2 pieces of fabric sew a line down them and then open it up you should be able to give them a tug without seeing any thread in the seam. Superior Threads I believe has some good info on tension on their website. Sorry I don't know how to explain it.