[M]y wife went out in the Tern, She said it felt faster, quote, "substantially faster", than the Coho. Do you knowledgeable types think this is possible?

Dan,
You're wife been pin'ng for your company? Spending too much time a'buildin' boats? Among the yachting set a fair hull is considered to be an essential component in winning races. Professional filling, fairing and painting the bottom, keel and rudder of a 24' sailor will set you back $6 to 7 grand. All the serious competitors have this done. It may only mean seconds a mile difference in speed, but that's what decides races.

Now see how reasonable your efforts are? Explain to the wife that you could really be afflicted like these sailors and your just trying to make her time on the water less strenuious. I guess the question you have to ask yourself is will it take more energy to smooth up the hull than you'll ever save in extra paddling effort?