I wouldn't ever have GFPT guys do a Nav without first passing the PPL exam and additional briefing work.. .. .Personally, I think it's a waste of time and money. All your attention should be focused on the General tasks at hand.... .. ....having said that, when I was teaching in Sydney I used to use a "nav" into the Sydney zone over the Bridge and CBD to motivate students if it was ever required. However, it was only short and sweet and didn't really call for serious navigation skills (and you could easily apply various GFPT exercises in the hour)!. .. .strewth, you're the boss. They should only ever be planning something if you told them to do it!