Thanks everyone, I appreciate the responses. I've gone for giving each player 2 points for a birdie, 1 for a par, minus any penalties they incur. This is pretty simple and will hopefully work out well. There will be a nice element of risk/reward for the first player. Should I go for birdie? Will my partner be able to match it? Should I play safe and make par?
Being able to drop a round is tempting Jim but I always feel we shouldn't win unless we play well. Ideally consistently well.
This also makes me almost allergic to unlimited Lonnie, I avoid them wherever possible. I always think they reward hours spent playing and many restarts more than they do good play.