Ed wrote:

The new set up gave a noticeable benefit in take off performance (and I do

mean noticeable).  However, the top end was relatively unaffected - although

I did measure an approx 4 mph increase in top aircraft speed.

OK; Ed – given your expertise on technical explanations, I’d like your take on why your increased hp resulting from the increased RPM is not giving you higher top end speed.  Is it exhaust back pressure or less than optimum prop, or other?

Al