Hi Michael,
By "4" I guess you mean feet , not inches!
Others have had a similar idea. Have you seen:
http://www.seahawk17.org.uk/history/index.htm#reedcraftand:
http://www.seahawk17.org.uk/history/jeckellsmemo.htmI have not yet come across the boats with the taller rig and will certainly look forward to any report from you on how things go.
Have you experience with river cruisers or other heavy ballasted and long keeled boats? I only ask as while making progress in a SeaHawk can certainly be frustrating amongst Broadland trees and the tide against you I have wondered if this might be a case of not understanding and accepting the nature and limitations of the beast.
I always remember reading a letter in a motoring magazine from a frustrated Mini owner, who'd fitted a three litre engine and was expressing disappointment that it wouldn't do more than 105mph. The editor was plainly amused that anyone should be so foolish as to think that power alone was the answer to making a car go faster.
Having said that, I was surprised about the reports of how a simple, and apparently minor, change to a rudder can make a boat perform so much better, as I would have expected the professionals to have had such things sorted after some 3000 years of development. See:
http://www.seahawk17.org.uk/boatshed/rudder.htm#fecklessSo what do I know!
As I say, I await reports with much interest.