I am also building a Fastrack setup. I will be using the Ws risers only going up about 2 inches for some depth on my smaller layout. My layout is a lazy L about 5 x 9 x11.
i purchased 2 sets of risers planning in advance to double them up side by side for Fastrack. I like that idea of glueing the foam boards to the sides for a finished look and more support.
gotta love these forums.