thanks for the info another q is how much cooling air does the motor need when cowled its going to go in VMAR PC 9 and the ill chop the bottom of the cowl so the Rocker covers are in teh air stream. The inlet is scale and is quite small how many Sq cm do you reckon? and i got a 12*6 is that ok for break in and runnig ? i'm thinking 13*6 when its all going well?