Thanks Chuck.
I've been doing some thinking :-) and have decided that the only way to go is with a round mould. To get the full use of the adjustable ferrule it is best to keep it round, as the oval dimension will not be correctly oriented if you change the blade angles. So now I am going to have to make two paddles, one one piece with an oval cross section and one two piece with a round cross section. I will give your foam suggestion a go. Hopefully I will succeed.
John K

: You could make an internal male mold out of balsa or cheap pink insulating
: foam.
: My sister has a paddle that I don't think is just an oval shaft on top of a
: round base, I think hers might be built with some sort of rotation
: pressure pulling the glass to the outside of a female mold.

: How do you mold