Why don't you just do this? Compute the mass of an 1/8" hardwood dowel approx. 3/4 of an inch long and then compute the outward force it creates traveling around an approx 3" circumference at 7000 rpm. Then compute the strength of the European beech (most good prop makers use this) from a point approx 1/2" in from the outside of the hub (on a plane perpendicular to the grain) and tell me what the liklelihood is of that dowel busting through that hub with that much force (the torque of the bolts) capturing it at the two ends of the axis. Then get back to me. We have a saying where I work... There comes a time in every job when you come to the realization that you just have to shoot the engineer and get on with the job! What field of engineering are you in and what do you work on, if you don't mind me asking? I stand corrected, an approx. 2.3" circumference.