I would still have a set of the Shimizu 575's rears just in case its really cold in the morning or overcast and the Yokomo's don't work.
Just stick with the mediums on the front and only change the rear tyres as the temp comes up.
As a guide for track temperature for a good track (temperature of the tarmac)
0 to 20 deg use Shimizu 575's
20 to 30 deg Yokomo's
30Deg + Ride R1
Some really grippy tracks you can get away R1's at about 25 deg, but you will have to test this out beforehand. When I am at practice before an event I usually wont change too much on the setup, ill just spent the time working out what track temps the tyres like for that particular track. Then tweak the setup from there.
I know lots of guys in the states like to use the 572's (hard) on rear, but on our tracks we either find them not soft enough to work and by the time the track temp comes up the Ride's are faster. The Rides work better when they are super hot, so I normally heat them up to 60 deg before a run.
Sorry information overload...