Just a little correction on this thread... The factory  demonstrator was a
320 with a Hartzell compact which had been shortened 14 inches...    My
understanding is that  this type of  "major" modification  to blades upsets
the harmonics and or dampening.  The ratios on blade chord length, width,
and taper ARE critical !

Lloyd Dunlap
Lancair 360
N214MM
230 HP
68 " prop slightly shortened Arrow blades
Beech Sierra Hub  HC-M2/YR