Hoping someone has some experience with this.
I'll be using MMF- I like to roll it out pretty thin using the "Mat"- but I guess maybe it needs to be a little thick. What do you think ?

I dont use The Mat but I do use choc BC under MMF all the time.

I use dark chocolate ganache under thin white fondant all the time, no problems.

Thanks for responding.

I roll my Satin Ice fondant to 1/8" over whatever kind of icing and it's fine

You do just need to take special care with any smudges or smearing of icing that may come out at the very bottom when you're smoothing. But it's absolutely possible and will be just fine.

I do it all the time as well. Just be sure that it's firm before putting on the fondant so that you don't get the smearing as much from the bottom. (just as kelleym stated). I covered a choco BC in a hurry and it was still very soft. Made a bit of a mess but was able to clean it up. Kept showing up on parts of my hand that I just didn't realize was there.

I do this all the time. My chocolate BC tends to be softer than my vanilla. So when I cover it with white fondant, I chill the iced cake in the refrigerator first to harden up the icing. I also lightly sprinkle the chocolate iced cake with powdered sugar before applying the white fondant.