Yes the innercrank bearing would allow air to transit from one side to the other, but the thing is there must be some form of seal between the crankcases as mentioned I have never split a crankcase on the 447 so not sure of the crank bearing and seal set up, I have looked at the parts manual but it is not really helpful, a mate suggested it might be a labyrenth seal (a bit like piston rings on there side), I know these were used in the konig radial two strokes, reasonably efficient at high RPM and very little drag.
I know I should ring the Rotax guru's but I'd be lucky to get any one to answer there phones for the next two weeks.
Anthony
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