Thought I'd just post this little tip for those of you, like me who use GWS props on smaller aircraft.
I've started using a GWS 6 x 3 on my mini swift recently (Park 250 motor) and I've noticed that if I use a prop saver (O ring type) that after a few days the prop starts to deflect (even when stationary) because of the tension being applied by the O ring, small white "stress marks" appear in the plastic. You can't put too large (slack) an O ring on there because you need that tension to hold the prop snug and centred.
To help prevent this put a couple of very small blobs of hot melt glue right at the root of the blades where they join the hub of the prop. You need to make the blobs as uniform as possible so as to avoid imbalance in the prop but I've found that you don't have to be utra precise - "close enough" will do as the glue is so close to the centre point of the prop. If the prop does vibrate add a dot more glue to one side or the other until it's balanced again.
This additional "shoulder" of hot melt also adds extra strength and prevents too much deflection when the prop comes under load.
You don't have to do this with a brand new prop (but I'd recommend it).
You can do this to old props, the heat of the hot melt normalises the plastic where its stressed and extends the life of the prop.
Hope this is of use!