Is the shoe sitting on a cake or is the cake the shoe.
RKT and modeling chocolate are quite different.
A lot depends on the size of the finished piece you are trying to create.
For a life size shoe I would use gumpaste, or a fondant/;tylose mix. Modeling chocolate accents maybe.
I would choose this because a shoe has to look sleek and RKT doesn't really lend itself to small and smooth with ease the way gumpaste does.