I would like to try flying with Graupner E-PROP 10x5 and 5mm reduction kit (http://team-blacksheep.com/products/product:123). 

But the prop mount of IRIS is too short for the Graupner props. The screws will not fully screw on the mount and It don't trust that setup.

What 5mm prop mount can I use with the IRIS that gives me a longer mount?

Would the "Propeller Fastener and Shaft Kit for blue motor" from 3DR (http://store.3drobotics.com/products/propeller-fastener-and-shaft-kit-for-blue-moto-1) work? Their webshop doesn't include any real specs which is pretty sad.

If anyone has an idea, that would be great.

Thanks!