Creative slider drag racing

This was my girls jet-skiing on sliders Saturday morning:

I feel one-upted, though, after seeing this bit of creativity:

I don't think my gym has any such bucket containers.  I've thought about having someone on a small mat in a hollow or something.

I've also wondered why Tumbletrak, since they sell furniture movers, don't design a larger slider to make it easier for more body part contact than simply hands or feet.