Hi David,
Sorry to drop the contest as I was feeling a bit under the weather. Initially, I was going in the direction of a logo for the boat, but then saw the contest had gone from a logo to an illustration. Doing an illustration would not be an issue, but since Logotournament only allows for vectors to be sold then I felt this would be very limiting. (Kind of like having a a boat made at a company the only works with wood. You may get a nice boat, but you can see how it would be limiting since no metal or fiberglass could be used.)
Also, there was a concern on what you had asked about regarding a 1:6 ratio. The illustration would be so small on the side of the boat that it would not have looked right. Depending on the way you planned to print this and the and limited seaworthy substrates, the drawing on the decal would only be about 10 inches tall. You would literally need to be a few feet from the boat to see it.
Anyway, I see that the contest seems to be going in the direction of the initial requirements, (and more a boat logo) than a picture of waters that the actual boat will be on in reality. I think this is a good move on your part albeit too late for me. :)
I wish you all the best.
Marcelo