ok, i'm sure this has been done before but i've got a carbon paddle in hand and a hacksaw in the other - need to know now.

broke my paddle surfing a few weeks back. bought a new one 'cos i couldn't even consider missing a wave. Now the boys have fixed the old one and i'm thinking to make the new one a surf specific.

So the old one is about one inch too long - way too long for the surf. how much shorter should i make the new one??

Also, it depends on the wave: a shorter paddle (your size or less) will be easier to handle in short, hollow waves.
For instance, if you find yourself having your paddle trail backwards on bottom turns rather than at a square angle, it means it is too long to fit in the wave curve.

It then depends if you want to forgot paddling confort entierely and use the best length while actually surfing (your height is a start), or want to compromise and have some length for confort while paddling (6" to 8" more). Shorter boards benefit more from shorter paddles.

Anyways, having 2 paddles(or more) of different lengthes and alternate between them is really good.