This is a question: In sewing a single-needle side seam, is one of the goals to make that seem as narrow as possible?
Oh. Someone finally comes up with a difficult one. Congratulations and a gold star. There are those shirtmakers who would argue in the affirmative on this one. However, I would disagree ... and probably win the debate because they are all dead. Nonetheless, there are two schools of thought, as follows: I make my two-stitch single-needle seams (usually referred to as the "closing" seam for it is the one which closes the sides and sleeve from the tip of the tailvent to the cuff) 1/4" wide and flat. This seam, and the difficult finger "turning" required to accomplish it, can be done using the fingers, lays flatter, does not dig into one's 'love handles', and can be pressed (ironed) to remove puckering. Others make their seams as your question reads, 'as narrow as possible'. The only way to accomplish this is with a special sewing machine foot called a "scroll" foot. Within this foot is a small scroll of metal (logic knows no bounds, eh?). The two pieces of fabric are fed through this foot and (sc)rolled into a tight little cylinder as they pass under the needle and get stitched. This has, for me, a multitude of downsides: Firstly, the foot is not accurate and the amount of material being scrolled can vary from 1/8" to as much as 1/2". Multiply this by the four pieces of fabric and variations in finished size of as much as 1.5" can transpire. Secondly, the smaller seam is not flat, it is a cylinder. This cylinder ... a rather solid one ... can pucker and be difficult, if not impossible, to press 'flat' - in other words, without puckers. Thirdly, because it is not flat, it tends to dig in to the side of the wearer under the trouser waistband (unless, of course, one is wearing jeans in which case one would look stupid to tuck it in). Wear your gold star with pride, untuck your shirt, and marvel at how many words can be used to not answer a question.