While the diamonds up would result in a flat surface, it may be that the reduced surface area of the diamonds will give more slip. On dock plates the diamonds are up to give the fork lifts a little more traction, but they are based on hard rubber tires, extremely heavy loads on a psi basis and limited room to move. There also is the effect of very short turning radii and heavy loads grabbing for all they can at speed.. Another factor for diamonds down is more material to scrub off before you compromise the integrity of the plate.

And it is pretty too.

Would be interesting to see if there is an engineer out there that could shed light on this.