Two and a half at the front, three at the back

Chris, can't help but wondering...if you increased tyre pressure on your one rear tyre, would that not reduce grip somewhat, since less of the tyre would be in contact with the road?

Grip is a function of the friction coefficient and resistance to tyre distortion, the grip coefficient is a fixed ratio determined by the rubber compound the components are force applied down v force required to break the frictional grip , for a road tyre its normally about 0.9 , tyre distortion effects how much the tyre will crab away from the direction of travel when put under side load whilst rolling and it's mainly influenced by aspect ratio.
As a summary
CoF determines the cornering force required.
Tyre aspect ratio determines the rate at which it will break away, an 80% tyre will gradually break away where the equivalent 45% tyre will break away more suddenly.

I went down to the 3.00 from a modern grippy 120 which was virtually all rubber in the centre, it was much better last time out. I will though play with tyre pressures when I next get to play. of course the harder front suspension helped too.

2.5" all round on mine.

2.5 front and rear.