I can only second what the others have said about using latex caulk instead of screws to hold down the track.
Another point you may consider is that, while Styrofoam is actually quite strong and does not break easily, it is prone to bumps and dents when handled. This can be avoided when you cover the surface and the sides with a 1/8" masonite board. That does not add much to the weight of your layout base.
Even wth a lightweight base, a 4 by 8 layout is quite a hefty chunk to be stored. If you don´t have the room for a permanent set up, there may be other ways to have a layout of your own.
Just as food for thought, take a look at this:
Mini-modular Layout
Though meant for N scale, it can be easily adapted to HO scale, if you increase the size of the modules to, say 1´by 2. This woulkd require to run a beam down the center for additional support.
I agree with the caulk idea. However, if you need screws for some reason, take a piece of track to your local hardware store and see what they have that will be long enough and fit through the hole in the base. My local independent has a wide variety of sizes. You could even make the hole a little larger if necessary.
Good luck,
Richard
Rather than using screws, how about acrylic latex (non-silicone) caulk. I think it would be more stable yet yet it is pretty easy to lift the track off with a putty knife if you want to revise the track plan. Of course, you will need removable sections where the track crosses the seam between the foam sheets.
Good luck.
I have lots of HO Kato Unitrack and no real space for a permanent layout. I have a 13' x 14' Laundry room
I can set up temp layout and run for a few days but must disassemble it and pack it up.
I am considering purchasing 2 x 1 ½” or 2” thick 4' x 8' sheets of foam insulation and screwing the Unitrack into them to make a layout I can store and easily set up to run.
I had an n scale layout and used this method but can not find the source for the screws I purchased?
Does any one know the size of screw I would need (at least 1 1/2” long) to fit thru the holes in the Unitrack.
If the screws are long enough and NOT over tightened they hold quite well.
I drilled out the n scale Unitrack but can't recall the size drill I used. I have drill conversion charts and several small drills but can't find screws long enough?
Any help or suggestions will be appreciated!