Dar, that 9,400 figure is probably right on, my old .46 MKII turns a Graupner 12x6 at about 9,000 but I preferred an 11x6 because with the 12x6 the midrange was very smoky, the HS needle could be set considerably leaner at higher rpm telling me that the airflow velocity (through the carb) was too low at full throttle at 9,000. The .53 has no issue like that.