RSJB18
I see you used the plaster cloth. I believe I will do a test run with the cloth really soon and use the foam like you show in the photos you have shared. In the background I see the Titebond glue I find a Lowes. I use that in my wood shop and I do believe that I can tell a difference when I glue boards together and then run them through the planer. I feel with this glue, the boards are not separating near the ends as with other glues I have used. Not as dangerous.
For my ballast I also used Titebond as well. My ballast dries together and lasts really well. So I can recommend that product. I apparently have missed those smaller containers when I am buying glue. I need that smaller type of dispenser.
I will watch to see how that you finish and color the plaster cloth when it dries! I believe I will use about the same amount of foam as you have when I get to that part of finishing off the exterior tunnel walls.
Thanks !