I don't think that's the cause of your rusty tank Andy. The filler should seal to keep the rain (and hose water) out and there is a drain to allow water to run out of the filler recess. The main reason for rusty tanks is condensation accumulated by parking the bike with a partly filled petrol tank. Over time the condensation collects on the bottom of the tank eventually rusting through it. You can also get some water from dodgy fuel.Should not have any probs Colin, the one place I would really watch out for is around the fuel cap,(as i found out a year down the line)