Work In Progress

However, Rolls-Royce as a company was not staffed either by morons or ingenues: its car painters were highly experienced in the priming and finish-coating of all generally-available engineering light alloys and steels, and understood exactly what materials they were working with.

FWIW, also Spitfire XIV G-ALGT https://abpic.co.uk/pictures/registration/G-ALGT has a nice photo of it in those colours, two doors down. For modelling purposes: don't expect to find the colours in a standard model paints range. I agree with Wellsprop: I'd just mix to whatever looks right. And here's a model built a few years ago.

I would say so. In Australia, or any other hot and sunny country, you'd have to be pretty daft to go out of your way to paint the fuel tank a dark colour when the rest of the aeroplane was a nice heat-reflecting yellow. Heat-soaked fuel is not happy fuel.

That's still not what the OP wants, though, is it? He's not trying to do an 8,000 lb cookie bomb bay - that comes as standard in every Airfix Lancaster II kit. He's trying to do a Tallboy Lancaster.

That is not the Tallboy bulged bomb bay, but rather the different bulged bomb bay created for the 8,000 lb 'cookie'

What are you using for propellers? the standard 120 inch diameter Peregrine three-blade props are much too small to absorb the power of the Merlin engines. Even with the fighter gearing you would need 129 inch at least, or 126 inch for four-bladers of the Spitfire IX type, and there is not a lot of clearance... Further to Dave Swindell's points on the centre of gravity, have you considered putting in a foot of extension to the rear fuselage where the parallel-sided section makes it easy to do so? That and the relocation of some equipment like the battery and radio equipment would be a big help in preventing it from immediately standing on its nose,

A sharp drill used carefully probably wont crack or break a screen - put a couple of masking tape layers over the place you want to drill, and rub down thoroughly, then the drill tip won't skip or scratch. Alternatively, a hot pin or needle (heated in a gas flame) can be a good way to make a small hole in a transparency (but practice first on a scrap unwanted clear part).

That looks so good I've had no choice but to order the sheet from Hannants!

In addition to the long-extinct Paragon conversion there was a 1/48 conversion by Iconicair in later years https://www.facebook.com/officialiconicair/posts/new-for-2021-is-a-148-scale-tallboy-and-bulged-bomb-bay-doors-for-the-hk-models-/6714593805282527/ I note that Iconicair's website is down so I dont know whether he is still in business. It used to be here https://www.iconicair.com/ Unfortunately the Tallboy doors are not the same as the bulged bomb bay doors for the Lancaster II. I don;t have any drawings but these threads contain information which may be of assistance.

Every WW2 radial engine in the 500 to 900 hp size and power class gets through at least 8 or 9 pints of engine oil per hour for normal operations, usually more like 10 to 12 pints. It's not leaks in the sense of loose oil unions or holes in tanks - that's just what the engine is designed and expected to consume, and almost all of that ends up coming through the exhaust and blowing back down the slipstream where it will collect on anything that gets in the way. Some is burned but a lot emerges as oily vapour which condenses on the airframe. When you see a photograph of a row of aircraft at readiness, especially bombers that normally do one flight max a day, then you are seeing an aircraft that has been wiped over. Even a little 145 hp Gipsy Major will get through one to four pints an hour -- I've had it right down to the tailwheel on a previously clean Chipmunk after an hour's flying without the later modified piston rings - and a 360 hp M14P does about the same. A big radial in the class of an R-2800, Hercules, Centaurus or R-3350 is more like 1.5 to two GALLONS per hour.

I strongly suspect it would not have been camouflaged had it arrived in the UK - it's rather late in proceedings for that - and North American therefore probably had no real reason to paint it in RAF camouflage prior to delivery. Yes, the RAF's XP-51F FR409 / 43-43335 was camouflaged, but that was significantly earlier in the war. There are no photos of the undelivered P-51H or any other P-51H in RAF camouflage AFAIK, so the Modelsvit instructions seem highly speculative.

Code sizes are whatever they were on the full size: scale is irrelevant

Ooh, this is fun! The Spitfire: it does look onscreen like P74x1 but those all seem to have led fairly unremarkable lives, so I wonder if it might be 7661 which does seem to have been at both RAE and A&AEE https://allspitfirepilots.org/aircraft/P7661

and from all other locations 😉

As far as it goes, though you could, if you wished, add permutations of round and pointy rudder on the IX sub-variants (pointy on all production low-backs, some high-backs). Oh, and there are also two different tailplane types, with at least three, possibly four different types of elevator (original horn, two-angle horn, revised section two-angle horn, and then the whole question of them being fabric-covered originally, then in some cases modified with metal-skinning, and some late production coming metal-skinned from the factory). Not to mention two different undercarriage geometries and three different kinds of mainwheel.