Hey Gary.
Foot? is that the downhaul? As I have been told that you require less downhaul the more wind and to pull it on when you encounter light winds. I realise that everyone will have a different version on this but is that the general idea :blush. I did have a 505 for a few years and was told to pull everythig tight in the big blows.
Maybe a slight misunderstanding on what you have been told, definetly more downhaul the stronger the wind, on a Mossie it helps bend the mast which flattens the sail, as well as opening the leech.
By talking about flattening the foot of the sail, I was referring to the need for more outhaul. Generaly the outhaul is increased with increasing wind strength also.
It is all about control and speed, if you can control the power of the sail with where your settings are and you are sailing fast, they are ok for you. But if you are struggling to control the boat and feel overpowered, flattening the sail should help with control and increase speed.