I have to agree with Harrie that this may not be a benefit.
If you have a stiff enough machine to stop it with a short you may be ok, but you say it slowed to the point where you could count the blades, that may be a significant speed and you may be making more heat in the stator than if you left it alone. Unless you can stop it to a slow crawl under all wind conditions it may not be safe.
If your furling works there should be no problem but for peace of mind in the occasional high winds it may make sense to actually stop it if the alternator can do it. You would be better to latch your relay so that it stays stopped until you reset it.
Harrie also has a point about throwing the stop switch when there is an instant of low wind.
I once shorted a big alternator at part load on my test rig, the forces are frightening and the loading on the blades and stator mounts must be such that I can't see it being wise to do this repeatedly from high speed.
Air X does this, but it is a tiny machine with little inertia. I wouldn't be happy without lots of tests to make sure it is a long term solution.
Flux