Last November, a friend tipped me off to the wonder of thermal underwear for everyday use. I don’t mean the long sleeve tops and long bottoms, but sleeveless thermal layers for your torso. Well, they are amazing and I thoroughly recommend them!
Just as some of my shirts got a bit shorter recently, so too have my thermal singlets/tanks. Buying the next size up would increase the armhole size without adding much length, so I took two of mine and sewed them together.
With a rotary cutter, I sliced off the hem of one and the top of the other (from armpit to armpit). I then pinned them together, matching the seams (which is why the lines are not 100% matched). Using a small stitch for knit material, I stitched around and was done!