If I recall correctly, DAZ shifted UV coords for the different Unimesh-derived characters in a couple of places, one of them being the nipples, others being the lips and navel, such that it's not precisely true that textures for Unimesh-derived characters are 100% perfectly interchangeable (without some tweaking.) If someone knows for sure that I'm wrong about this please feel free to correct me. You said you'd already tried working with the areola morphs, but if you can make the auriole larger to roughly match up with the texture, that might help. I'm pretty sure that what you're seeing isn't that the texture is stretching, if you have M3 you can test that. I think I've seen this same thing before when using M3 textures on David. Best of luck with finding a fix!