Also depends on the track.... the track I race at its better to start with full rears (crc pro-cuts) and you can race em untill they hit the 43mm mark.
From then on the rear will be unpredictable at certain parts of the track.
On another track I know, anything above 43mm will make you flip...
What i mean with this is, dont be dumb and true all the tires you receive to 43mm cause it can seriously backfire!
Make it idiot-proof, and someone will make a better idiot.