If you plan on using the WS foam as the base, I would suggest insulation foam available at Lowes, Home Depot, or the like. Price the two to be sure. I got mine at Lowe's.
The WS foam inclines are very nice. I used them on my last layout. Easy to cut, curve and glue. If you want a 2% that is what you get, no measuring.
Good luck,
Bob
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