@Grey Wolf
Without a really strong indication of narrator shift it would be completely awful.
Once the reader became aware of this, it became obvious when I had this happen. Most normally, I would throw in the word "change". Which when reading the first chapter most assumed meant changing clothes. But after chapter two, became obvious that meant they were changing bodies.
Plus other things, like Chris wore almost exclusively dresses, and Bohica of course wore jeans. So if the character talks about a bra, it is the female. If they talk about their boots or jeans, it is the male. Or even the embarrassment if she changed and ruined her clothes as she now was over 50% bigger, a man in the remnants of a size 4 dress. Plus they did talk differently from each other, and even act differently.
But it was obvious every time that happened. I would write something like "I went into the back to change, and was soon up on the rooftop heading towards downtown". To any reader, that tells them right away that Chris did not change just clothes. She changed into a big man almost 7 feet tall, who thinks nothing of jumping from rooftop to rooftop.