The stator holding design is very robust (story here http://www.fieldlines.com/story/2008/8/18/83321/8140), and I have shorted the phases out at high power levels (1.5kw) just to see how the braking works. No sound, instant stop..... but I was a bit reticent about shorting out over 5kw, and thanked the wind for a lull (not much but enough to calm my fears).

The stator is thick, and the 9 x 1/2" thick bolts probably would have taken it. An added difference I did was to mount the front magnet plate directly to the front of the bearing holder flange, which shortens the length of the stator bolts considerably, and gives a better chance of controlling the stator torque without too much bolt bending. It is very stable under shut down with no shudder at all.

I will make another one with longer mill to pole offset to get more control of the yaw torque for this application. This ones temporary tail is very light, so not much room to move with this one.