As it is work in progress it has not had the satin or matt varnish applied yet,

Wartime aircraft did not have a coat of varnish; that was post-war. Squadrons had Aircraft Finishers, who were advised to do any necessary retouching, then sand smooth with wet-and-dry paper, followed by a wash over the whole airframe with clean water. The glossy patches under that aircraft have all the appearance of pools of water, which one could expect if it had been subject to a “bull” session before the VIPs arrived.
Any pilot who had his aircraft wax polished went totally against the advice of I.C.I. (who trained the Aircraft Finishers,) since the wax soaked into the paint making a retouch impossible, so that the whole paint had to be stripped off, and done again.
Early Mk.IXs, which were converted from Vc airframes, often retained the old-style walkway lines of the Vc; later aircraft had the usual “backward L” on the port wing, but also had a mirror “L” on the starboard wing.
As for getting at the fuel tank, that had always been possible from the port walkway, and groundcrew tended to lie down (thereby spreading the load) when they needed access to the wingroot fairing.

And the previous poster mentioned that this area of the wing was altered AFTER the second radiator was fitted.
Which was on the PORT side.

So they took the opportunity to make the top surface of thicker material on both sides.
On early marks it was 24 s.w.g; on the IX, and other later Marks it was 20 s.w.g.