All speeds for aircraft have been historically continually over stated. Unfortunately it's no good quoting manufacturers/ RLM figures, as these were for new ac, without full equipment and had not been flogged to death during war. All manufacturers want the customer to see the best figures (ever got that MPG or top speed they quoted in your car?). The figures I've quoted are just ball-park general figures based on years of reading and research, using first hand accounts, biographies etc, as you've used, and from many many reads of ORBS and claims report from the National Archives, from NF encounters and bomber squadrons. I'm not saying my figures are exact (I'm no expert), but I think they are far closer to the average real speeds of the ac.
It all depends what source of figures you use, but Brown (Wings of the LW), yes, states he gets 400mph out of a G6. But that's a almost certainly a 213 engined G6, which there were few G6's produced and very few fitted with the 213 engines. The standard late G1 with 801's would have an
manufacturers original top speed of about 344mph, add on full equipment, crew etc, and the real figure would be....?
As for Brown's flight in a 110G4, he gets an eyebrow raising 368mph(!), where everywhere else states about 342mph max and a max cruise of 317mph. Pilots would not fly around at max anything, as engines became so tired/unreliable, they needed to loitre, so economic flying was vital. It's not about how fast, it's the stern chases over many miles. If a Lanc is going home from Berlin, flying about 200mph, and the NF flying at 250mph, and 100 miles behind (having not been in the stream), he would catch it up at, say, the Dutch coast, or at 300mph and he would catch it at Osnabruck..200 miles away. They couldn't flying for long periods at high speed or max cruise, as engines regularily overheated and failed. Obviously if in the bomber stream, then all you need is a small excess of speed of the target, that's why the experten were so keen to get off first, and get good indications of the target and direction of the bomber stream.
I like your speed settings for the ac you quoted, I think very reasonable, but they are max speeds (which would rarely be used). Who know's for sure!
Just one shelf, I'm sure you have the same library....ha ha!