I have done some more flying, adding another 2.5 hours. For the last hour I added another 3° degree of pitch (i.e. total 7° more than with the 532). It made almost more difference than the first 4° degrees. I can now outrun my airspeed indicator at level flight (limited to 150 km/h - 93mph)!
With cool air just after the rain I still have a 6050 RPM maximum. Comfortable cruising speed 110-120 km/h around 4800RPM.
Takeoff is still very good so I will try another 1-2° pitch before doing serious fuel consumption estimations.