: Dan- Thanks for the great info to the link you suggested. Sure enough I would
: of followed the picture in the book and made them upside down.

You would be hard pressed to make the blade shape upside down, because you can always switch sides when you are in the boat. This serves to flip over which is the upper edge. The mistake you can make is to have one blade oriented one way and the other the other way. In this case you would always have one blade "right" while the other is "wrong"