? Most folk aren't using foil backed sheets, or even that type of foam. Most use the bare "blue, green, or pink, " close core foams.
You should consider another thin layer of another foam over that one...??
Aside from that sanding might work better, or make a bigger mess...??
A grass mat wouldn't care about being glued. A few ripples and bumps actually form nice terrain, throw down that candy wrapper and cover it right up with a grass mound 
I guess it depends on what your plans were.
