Hi Dangermouse
Yes, I tried that combo, although I didn't know I was at the time. I took my wheels in to a local dealer and said "Pilot race please" after I had a blowout on the motorway. After I had put 100 miles on them, guess what...another blowout!! then I noticed when looking at the bike on a trialer for the second time in a week that the rear was a sport and the front a race.
I noticed that when the tyres were warm that the bike wasn't as stable in a straight line or mid turn. I only managed 100 miles on the set, but I would say not to mix....Michelin certainly don't advise, as some pipsqweek kept on quoting at Carnells...
BTW, the trackday at Cadwell was a blast, thanks for all the tips. Have booked Snetterton, Thruxton, and Silverstone. When and where are yours? maybe we could meet?