Sorry i misremembered about flat rudder vs profile rudder in the article.
I thought it a very interesting read even though i suspect the author would simply curl his lip and sneer at the very idea of a flat plate rudder on a yacht!
Nonetheless, the turbulent drag from a flat blade rudder could cost you significant and measurable speed. The difference between 5 knots and 4 knots is an extra hour over a twenty mile passage. If your boat is already not a fast boat why would you want to handicap it further? i would be looking to make the most efficient rudder i could.
Just my opinion and the one of the great things about owning your own boat is being able to do with it as you please regardless of the opinions of others.
Good luck
