Different researches have drawn different conclusions regarding McKnight's Hurricane. Vintage Wings of Canada did a lot of research before painting its Mk.XII, but I disagree with some of their conclusions.
Just a few days ago, the fuselage of the Vintage Wings of Canada Hurricane Mk XII was pulled from the paint booth wearing her brand-new markings—those once carried by a Hurricane Mk I flown by Canadian Battle of Britain ace Flying Officer …
www.vintagewings.ca
They opted for a scheme from between Nov. 1940, when the sky fuselage bands and spinner were applied, and Jan. 1941, when McKnight was killed. They are likely correct that P2691 received the sky spinner and band during that period. However, McKnight wasn't very active and wasn't scoring kills during that period, so I agree with you that Sept. 1940 is the more appropriate time to depict the aircraft.
Personally, I think that the roundel would have been repainted as the 35-in Type A1 rather than being left as the 35-in Type A with a 40-in yellow disc, if indeed it ever wore that roundel. I am not convinced that the squadron's aircraft in Sept. 1940 still looked like they did during the Battle of France, when the pics of P2959 in VWC's research were taken. I think that both the roundel and fin flash were reduced in size by then. That's what I went with for the model I built, which is meant to represent the Sept. 1940 time frame.
One thing for sure, the proportions of the blue, white, and red circles are wrong on the AH and the roundel on Hurricanes was always painted low on the fuselage, within a couple of inches of the upper/lower paint boundary. So that's one thing I'll correct on your skin, also I'll substitute the unusual "A" code shape which is one of the few things actually documented about P2961. Whether to put the boot-kicking-Adolf motif on the cowling is another point of controversy. Vintage Wings decided to put it on theirs, but I don't believe there is evidence that it appeared on any airplane other than LE-D and it might be a Bader personal marking rather than a squadron marking.