The 2" Styrofoam creates a problem. It won't hold fasteners. FasTrack doesn't move much, so a screw here and there would be enough. The curves are where the push will be.
The FasTrack holes are pre-sized for a #4 screw. Hard to find in bulk. The #6 with the hole drilled out to 7/64" is the next option. Hard to find in a 2 1/2 length.
So, drill the hole out to 1/8" and use #8 x 2 1/2" drywall screws here and there. Those screws are easy to get in small quantities. There is enough plastic to drill out the hole to 1/8".
Other than that, let 'em float or press them into the foam a little.
That's my 2¢.