I like the look of larger stitches, so I always use 4.5 or even 5. I find that this stitch is small enough to hold all layers securely and if you have to rip, it is not impossible to remove. I also find that the Janome walking foot tends to automatically use smaller stitches over thicker areas. Perhaps if I had the thread regulator option, this wouldn't be an issue. Experiment and see what works for you. No one is coming to measure your stitches and complain!