[Andrew Rowe]

Thanks Des, following on from your feed back and from more investigation, the length should be about 1185mm and the timbers are 42 1/2" long, and stop on top of the tray. I conclude that the tray is a separate item and as you say a tight fit on the fuel tank and then you would slide the whole lot down the hole and then push the side packers in , until they touch the top of this tray.
Just thinking out loud.