Making a woman sound more like a man with formants is a lot easier than making a man sound like a woman. There is more to singing like a woman than pitch and formants. Women sing a little less throaty, a little more breathy on average passages. They aren’t as gutteral - consanants are a little softer. Also, men trying to sound like women often overdo the whole feminine vibe. The differences are most often very, very subtle, yet obvious to all listeners. It’s extremely difficult to pull off unless your voice (and psyche) is built that way. There are a few male singers who naturally sound feminine. That helps a lot.
Maybe also try pitching it down a half step before singing, then pitch everything, including the vocal back up that half step afterwards.
Just shifting formants up will immediately make you sound like a chipmunk.
Not trying to say you shouldn’t do it, just trying to set you in the right frame of mind.