So then the choice was between the new square-shoulder V710 or Hoosier A6. Since almost half the season is alreayd gone, I've decided to give Hoosiers another try.
An I must say, I'm impressed. There is no abruptness at the limit, there is a very good feel of the slip angle increasing before the wheel starts to slide (and I think I haven't got it sliding yet). I guess, the previous issues I've had with Hoosiers were because the tires were old, and maybe also because the shocks setup was screwed up big time.
An interesting thing is that A6 needs a different pressure difference than V710. I've been playing with the rebound adjustment on the shocks and got it sorted out that on V710 the same pressure front and rear worked best. But on A6 the car felt understeery. I've been so impressed by the good grip of the new tires, that I didn't notice the understeer until the end of the day. So the next event I've played with the tire pressures. 4 psi difference seems to be the charm. We'll see. I've got another event before the National Tour.