I agree with all that Maglar says, especially about your good work on the kit. But the bit from the rep about the 'improvements' from Dragon is fantasy, and smacks of cover-up excuses.
First, neither Airfix or Tamiya produce a 1/32nd scale Mustang, or even any parts common, and second, months before this kit was even released, Dragon announced that it was being produced with their own 'slide-mould technology', and that it was 'all new'. Don't know where the rep got his info, but the same faults are obviously present, and some of them are blatantly obvious in the pics!
Personally, I think that perhaps some of the tooling might have been contracted-out from the start; the pre-production test shots, possibly from a (short run) master-pattern for the moulds, would have produced parts that fitted well, as seen in the original, unpainted advertising model. But, when the production tools were used, probably at different locations, and the parts all came together, those from (for example) 'Tool A' didn't meet-up with the ones from 'Tool B' that they were supposed to match. This is more likely in line with what you were told by the rep, who probably quite innocently thought that it was an error due to the diverse manufacture, import of parts etc. The bottom line is, the kit is flawed, and it doesn't appear to have been corrected, which is not all that surprising, considering the huge cost of producing moulding tools. Shame really, as the kit does eventually turn out looking OK. But, just think what it would have been like if it was right in the first place!
One thing I've noticed that might support my theory - the latest variants of the kit, under the guise of a recce version, and, I think, a Korean War period version, are quite a bit cheaper than the original P51D you and I bought.
But, back to your build, and thanks for the explanation about the latest IPMS set-up. Looking forward to more progress shots mate.
Terry.