that was our problem. we had to get the thickest plastic mat because the ones specifically for office carpet are flexible as fuck. a thin sheet of plywood (we have a few pianos and soft “hardwood” floors what get grooves in them when you drag a piano across them, and a thin sheet of plywood protects the wood from the piano. i imagine the same plywood would work great for this if you could get at least > 1.5m x 1.5m sheet. it was just easier to get the plastic.
that was our problem. we had to get the thickest plastic mat because the ones specifically for office carpet are flexible as fuck. a thin sheet of plywood (we have a few pianos and soft “hardwood” floors what get grooves in them when you drag a piano across them, and a thin sheet of plywood protects the wood from the piano. i imagine the same plywood would work great for this if you could get at least > 1.5m x 1.5m sheet. it was just easier to get the plastic.