I did not noticed that much difference to be honest Tav,running the crapy slicks I had on the front axle and R888's on the rear,than having a good set of R888's all round.
I am sure a new set of good quality slicks all round would make 2 to 3 seconds a lap over R888's,but the last time we went to Cadwell over the winter on R888's and I was lapping in 1m 50s,on wednesday evening my best lap was 1m 48.5s,so only just over a second difference,that gain I put down to track temperature,infact we are going back there on the 6th of July,and Ive just ordered a couple more R888's,with them fitted I am sure I will be a bit quicker than I was on Wednesday,we shall see