Cicero wrote:

==================================
Google pictures suggest that it's on castors which in turn suggests very
localised loading. It would be worth considering some kind of load
spreader made from material other than wood which can't be
easily penetrated or indented by pressure.

Cic.

Indeed, the load is on castors and that would amount to considerable
point load as you suggest. The piano is presently standing on castor
cups recommended by Steinway that spread out the load to 6" circles.
They are, I believe, made of some sort of plastic.

Thanks

Steve