I'm not sure I agree with you. I wear a size 42 from western makers. I don't fit a size 42 from most Asian makers (chest too tight, armholes too tight). I don't know about TFH's sizing, but knowing the actual measurements will certainly be helpful in deciding whether I'd need a 42 or a 44.
I agree and that's why I mentioned that the correct size number for the Flat Head is certainly something in a need of verification since being based on an Asian built, there's a possibility that your regular size might be off - but - I strongly believe that for anyone buying their first jacket, correct measurements will do more harm than good.
I mean, knowing the numbers will definitely be beneficial for you or me but for someone who's only just measured their other "good" jacket, there really is no reference point that can only come after, well, years of trial and error.
One thing that I'm absolutely sure of is that if the P2P works, so will everything else. I have NEVER tried on a jacket in the correct chest width, that had some other measurement off (except for sleeves but that's another story).
There's already some talk about the length of the jacket up there and that's... Well, the jackets are OTR so there really is no point. I'm sure that the length will be okay, provided the rest of the jacket checks out. Simply because there's no alternative.
To simplify things even further, with OTR, it's just like Goldilocks and the Three Bears: One jacket will be too roomy & baggy, one too tight & uncomfortable and one will be just perfect.