Waving from a safe personal space near Seattle.
T-shirt quilts are a skill unto themselves! Some people love them and do wonderful things, I'm medium-indifferent and avoid making them if I can. They are, however, a wonderful and appreciated gift even if just to ourselves.
Did you fuse a lining to the t-shirts before cutting? Most people first fuse or rough cut the shirt into halves, then fuse the interfacing, and then border the units with some sort of straight weave quilting cotton.