Some extra pressure helps stabilise the tyres under hard (and bumpy) cornering. It also has the side effect of making the handling sketchier. The surface is fairly slippery anyway, and I was surprised by how little stopping power I had.
A couple of the RX8s that didn't add pressure (or had aftermarket suspension doing funny things?) wore all the tread off the shoulder of the right front tyre. They were going at it hard, but it was a shame to have toasted tyres with good tread in the middle. A few extra psi like Angelina said might not go amiss, depends on wheel camber and what kind of lead boots you wear.