It was probably to save the petrol in the tank. It's now NZ$1.53 for 91 octane, and will certainly be NZ$2 / litre before Christmas. This Hurricane Katrina means oil prices will probably be $80/barrel within a month.

RE; the plastic bracket. I pop riveted mine on using all eight holes, and the fire extinguisher isn't that heavy.

But certainly very cheap insurance. You'd think you'd get an insurance discount, wouldn't you?