Track underlay installed

I decided to use relatively cheap sill seal foam to lay underneath the tracks in the hidden areas.

I bought the underlay at Lowe's -  5½" Sill Seal Roll Item #: 13281 and it comes in 50' lengths.
I stapled it to the plywood and then I placed some track on top of it to temporarily get a feel for how the tracks will look. Many of the tracks shown here have the Merkur Styrolplast ballast in place - I will use that in visible areas.