Spinner, aluminium or fibreglass? Safety?

I'm trying to select a suitable spinner for our Rans S6S. Besides looks,
weight and airflow I'm a bit worried about safety. There are several options
in terms of material and mechanical construction, and I'd like to hear what
experience you have with any particular type. One thing I'm wondering about
is that many spinner backplates are sandwitched between the propeller hub
and the propeller itself.

I read somewhere that the power transfer to the prop works by means of
friction between prop and hub. The prop bushings are only there to center
the prop. If that is correct then introducing an extra layer between the
prop and the hub can have profound impact on power transfer. Unfortunately
I've been unable to find any documentation on this subject at all.

Any thoughts??

Rob