So the hole is for the fuel tank to come through. I was a bit concerned about water and the like getting in. I thought that there may be a panel that had come adrift.
Ah Stuart, this is Lotus. Although it's highly likely that bits can and do fall off, in this case they decided not to put them there in the first place !
My covers aren't what you'd call glowing examples of engineering, but they do work quite well at keeping the petrol pipes and tanks clear of dirt and water spray. They are made from 2mm Aluminium, the first generation were 1mm and a bit on the flimsy side although they worked well enough.
On the photo, the green is GRP floor, the red Al and the blue either rivets or bolts. The photo shows basically how they fit on, at the front leading edge there is a pop riveted panel which simply slips over the fibreglass and lodges in place. At the rear there's 2xM6 bolts which pull down another internal panel to hold it all secure. It looks a bodge job, but it's quite sturdy once in place. If the M6 bolts are long enough you have sufficient "wiggle room" for the internal plate to slip through from underneath, fitting them in place is a one-side job.
Brian