I am making a Top Hat cake for next week (3 10" cakes stacked - I might trim in to get a slight concave look). I will be using choc MMF out and rolling it around the cake (not covering the top) so that the sides don't pull down (make sense?) and tear.
Should I use BC or RI for the layer between the fondant and cake? I've seen people use RI (even saw Duff use it once) and they say it works like spackle for fondant and holds it up against the cake but didn't know if anyone here has used one or the other and what results you got. (here's a pic of how the book shows the fondant being rolled on)
I always use buttercream under fondant. Royal will harden, and is not very tastey.
I would use buttercream, it is much tastier and unless you adhere fondant pretty quick your RI will harden and fondant will have a hard time sticking to it.
just an added note..........you could use a dab of royal to stick fondant cutouts or shapes to a fondant covered cake.