Probably 1/2 the a/c in AH cant get their published max speeds.
I cant get 448 out of a Spit XIV either, or 408 out of a Spit IX. Ammo mentions the P-47D-25 as well.
Operational a/c did not have the performace to get those published speeds anyways, and thats true with all of them.
Published speeds are the product of optimal testing with test pilots at the controls, not operational models with ammo and full gas, that are being used daily on ops for real combat missions.
Eg, the P-51D supposed to do 437mph, well, I doubt most 8th AF Mustangs that were flying in 1944 would ever hit past 425 in RL, with an operational configuration, paintwork, ect.
I would view them as an "approximation" of expected speed, not a bible.
445 for a G-10 is all of 6mph off the mark, pls dont tell me that would make any difference, in any fight, ever, in AH. I wont even get into the subject of published speeds for the G-10 (already have).
I can get 440 with a Spit XIV, again, all of 8mph off the mark, that is close enough to be believable for me, for an operational fighter.
If its significant, I would say fix it (any of them) but not such a miniscule figure.
Regards.