INTRO: I made this thread to sort of neatly compile all the data/information over in the BodySlide Conversion Thread into a neat little guide to encourage more of you to use BodySlide and Outfit Studio correctly! The following link is all you need for most of these tutorials, it also contains official tutorials and FAQ on the main page. BodySlide 2 and Outfit Studio Fun Fact:
CREDITS: Caliente - Creator of BodySlide and CBBE body cell (ousnius) - Contributor to BodySlide. You can ask him
I just asked Expired, he said RaceMenu picks the first shape with a skin shader (body), not the first one in the list. The only way this could happen is if you have two bodies inside of the same NIF, and the upper one in the list is bigger than the lower one, Then you're not going to see your overlay.
So, did you make sure there's only one body shape in your final NIF?