Fuel tank level during storage

[chpprpilot]

Moomba: At what fuel state should I store my boat. Not long term, but during the week while I'm counting the minutes till I can get back out to the lake...about five to 14 days.
The reason I ask is that my last boat, a 2000 Outback LS, I used to keep the tank full between weekends to prevent the tank and components from rusting while sitting empty. However, over a particularly hot week, the fuel in the tank expanded and came out the vent onto the gelcoat and stained the gelcoat permanently.
After a weekend of use, is it necessary to fill the tank for corrosion prevention or can I wait until I'm heading to the water to fill her up?

[jburnside]

If I'm not mistaken all the fuel cells in our boats are plastic. I'm certainly not an expert on oxidation but I think you're probably OK with less than a full tank. I would be more concerned with possible moisture absorption and ending up with some water in your tank.