XPS for topping ply baseboard?

[centenary]

Been watching Larry Puckett's DCC Guy You Tube vids and a few other US model railway (road) builders.

Larry's full layout and UK exhibition yard build, uses a wooden frame with plywood top. But then he lays XPS, extruded polystyrene foam sheet about 25mm thick on top of the ply. Mainly as a sound deadening material but also good for carving details such as small rivers or drainage ditches etc.

Anyone used XPS over here on top of ply instead of cork etc? Thoughts?

[Bufferstop]

I've not used it over ply so can't tell you if the sound deadening works. I have used 50mm rigid insulation for small baseboards with no other framing just 3mm ply facings all round (Points operated by wire in tube buried in surface.) I still have one 15years old and still solid.