Prop Pitch Question

Hi All

I fly a Pazmany Pl-2 (see link below for pictures) that had a power upgrade
from an 125 h.p. O-290 to a 160 h.p. O-320. I fly behind a McCauley Metal
prop. After the engine change, I had the prop repitched from a 7063 to a
7067. Top speed increased and my initial climb rate is about 1400 f.p.m. I
recently changed the plugs and magneto leads and saw another 100 r.p.m
increase in straight and level flight to 2900 r.p.m. I'd like to increase
the pitch of the prop some more. A basic rule of thumb is a one inch
increase in prop pitch will reduce the r.p.m. by about 80. I figure a 3
inch pitch change should drop the r.p.m to around the 2700 mark.

A fellow in the next hangar flies a Thorpe T-18 with a severely pitched
wooden prop. He told me that he can only achieve a top r.p.m of about 2450
r.p.m. behind this prop.

My question is this - Is this common to pitch a prop so that full r.p.m.
(2700) can't be achieved? His plane has shorter wings and is much sleeker
than mine (same engine), and about 30 m.p.h. faster in top speed. What kind
of top r.p.m. are all those RV-6/7/8/9 flyers achieving with their big
pitched props?

Any advice would be helpful. I'm sitting on the fence. Go with a minimum
pitch increase to bring the r.p.m. to around 2700 or go with a bigger pitch
increase for a real airspeed increase.

Blue Skies

Eugene
http://home.cogeco.ca/~pl2/paz3.html