Heh funny you mention the A539... Last time i was at knockhill as a passenger in my mates 1.6 Nova it was slightly damp, we were at one point lapping behind a race prepped 'locost' kitcar. The power to weight ratio of both cars must have been almost identical, as there was very little in it on the streights but thru the corners the locost was squirming all over the road and it was really hampering our times, finally managed to get past thru some crazylate braking and properly left him behind thru the twisty sections.
The nova was on Uniroyal Rainsports, and the locost was on A539's, and given a locost really should be able to trounce a nova round a track, it was clear the tyres were seriously hampering him
The rainsports really impressed me as a road tyre. They're perhaps marginally less grippy in the dry than an eagle f1, but in the wet they are simply awesome, and remain extremely progressive and provide tonnes of feedback.
A mate of mine tried the KU31's, Eagles and Rainsports back to back, and he recons that Eagles got the top spot on a warm dry day, with the Ku31 and Rainsports coming a close second. In the wet, the Rainsports were the best, followed by the KU31, the eagle was odd in that he found it good, perhaps even beating the KU31 on a damp road, but hit anything resembling a puddle and it would result in a complete loss of traction, which in his view made it quite dangerous, as it meant it felt you could push on a little faster than you would have with the KU31, but he felt he couldnt trust them because hitting a puddle while near the limits of grip was very nasty.