I have found the front really dependent on pressure selection. The difference between 15psi and 20+psi is huge. The problem is running too low and dinging the rim, 210+90kg is a fair load to hit blunt edges at speed. Having said that, the sidewalls are really stiff and do stand up to abuse pretty well. I usually run 22 front and rear as a compromise when I can not be bothered to take the pump, but I know what you mean with the front at that pressure, very sketchy. I will give the Pirelli MT 21 Rallycross a go on the front next time and see if that is a better match up with the 606 rear.