Thanks for continuing to check into this. I briefly considered a tshirt, but just now when I tried one on with the sweater, not only did the scoop neck not look quite like what I want (although in a pinch it will do), but the sweater's sleeves are so formfitting that the tshirt sleeves bunched up.
I appreciate all your research and ideas and will look forward to your next suggestions. This may seem like a lot of fuss over trivia, but I recently lost enough weight to have a shape again and this amazing sweater makes me look HOT! I haven't felt that for too long. So I'm eager to wear the sweater in as many situations as possible.