Just a little history about Hartzel props on a 360.  We had two accidents
that I know involving prop separations on 360's.  One involved the much
photographed  red factory Lancair which resulted in one fatality.  Another
involved a blade separation with the engine mount bending and loosing part
of the cowling.  In this case the pilot was able to get the Lancair on the
ground even though the visibility was near zero due to oil all over the
canopy.  Keep in mind that a prop separation is bad because the visibility
may go to zero and the CG will move way aft of the aft limit.  There will
be other minor problems to deal with too that are obvious.

It is imperative that the prop/engine be matched to prevent harmonics from
destroying either especially with the heavier metal props. Lancair provided
this testing and the results are well known.  Stick with the tested and
approved engine/prop match else realize you are taking additional risks.
Also realize that even an approved match may have some MP/RPM limitations
as is the case for the 360/68" Hartzel combination.  

James B. Frantz
Proprietary Software Systems, Inc.
www.angle-of-attack.com
LFrantz@compuserve.com
(952) 474-4154