I feel your pain, I'm not a futa fan AT ALL. I've tried setting it to 48% male, 1%futa, and 51% female and it still leads to a very large amount (likely more than 1%) but if you're willing to take the time (and it WILL take some time) and cheat a bit, you can view who's who when they're in your area and change it. Simply go into the debug console, go to current location, then match the green names from the area to their name in the console: click body parts near the top and remove penis size and testicle size, then go to gender a little lower and switch from Futa to Female and you're good to go. Rinse and repeat anytime you see Green in the area your in. I would just avoid doing it to either of the custom Futa's (the editor and Sierra) just to avoid breaking anything in game.