I used this type of foam insulation before but never for modeling. I was thinking of fourming a mountain hardshell then using the foam to fill out the mountain(tunnel) Has anyone ever tried this? Thanks.
If you are following the Woodland Scenics method, you build and shape your mountain with the foam (extruded blue or pink foam), then overlay the foam with the hardshell plaster/hydrocal (plaster cloth or plaster dipped paper towels).
I am in the process of doing this. I am still shaping the foam on my layout at present. However, I have build a small diorama to test out this method, and it seems to work real well.
You might want consider laying the track where the tunnel will go, then building your tunnel over the track, and finally building the mountain over the tunnel.
Dale B.
I kinda like a lot of room in my tunnels as it allows for easy extracation in the event of derailments.