Extending the kidney piece, how should it look? (Bobamaker armour)

I have a Bobamaker armour, and I need to extend the kidney piece to make it reach the cod piece. I'll be using abs as a foundation and fibreglass on top of that, I think. But how should I shape it? It is kind of round at the ends, so there's no way to extend the lines in a good way.

http://2.bp.blogspot.com/_hAjHhJbaTs...0/P1010137.JPG

I would ask Daz what he thinks being he made the stuff...Im sure he could tell you what will work with it