As Ashley says there is a corrleation with Vo2 max and Skinfold – so there is a factor there.
I must say I’ve never encountered a case where more bodyfat is an advatange in any sport – (once it’s not below 3% or something!)
One point that is important to bear in mind (in my opinion) though is that while higher body fat is a disadvantge … aiming to reach unrelaistic goals of body fat is an even greater disadvantage. I’ve seen many cases where the athlete concetrates on the skinfolds more than performances.
I’ve done a lot of work on body fat in fact studied thousands of skinfolds in rugby, position specific, rates of decrease and standards for elite players… there are certainly patterns and some interesting ones.
It is good to have goals and to have targets for each position – for example a back should be getting close to a sprinters body comp (9-7%) as it is very similar in demand.
To be honest the whole area of Body Composition (or Anthropometrics as I now refer to it since I’ve started to try and look at girths also) is very interesting especially when you look at the influence of hormones on bodyfat sites, Estrogen & Bicep, Insulin and Supscap etc etc.
But for practical pruposes it’s very simple – stay lean & get stronger … the actual figures (within reason) don’t matter too much.