The Hasaegawa is an old kit, but goes together well. It might have it's origins in the 1960's 'Frog' kit, judging by the seat, which bears no resemblance to a Mustang seat, of any Mark, and is common to the ex- 'Frog' kits used as early Hasegawa releases.
However, apart from that, and the usual Mustang kit errors around the cockpit area, in this case being too wide, it makes into a nice model, if a bit simplified in some of the detail areas. These, in their day were quite advanced.
The Dragon kit is very good overall, and makes a beaut model, it's just a pity that they spent so much time designing gimmicks such as the working suspension on the gear legs, instead of concentrating on fit of parts. The much-publicised incorrect and heavy rivet lines is nothing much to worry about. From what I've seen, having checked mine over, there isn't much wrong with the layout, and they look acceptable under paint. The biggest problem is the fit of the internal parts - they don't!
You'll need to build a 'shelf' for the cockpit assembly to sit on, as the floor doesn't reach both sides of the inside of the fuselage. On my example, I'd intended to build it so that the cowlings could be removed to display the engine when required, but had to remove the carefully assembled and painted cowling support framework in order to get the cowlings to fit, and then glue them in place, and use some filler !
A really excellent feature is the K14 gun sight, which really looks good, but there aren't alternative parts for the earlier sight, used up to late August '44 and beyond.
In general, although the instruction diagrams are quite well produced, there are a few 'vague' areas, with, for example, the brake lines shown the wrong way around, and the location of the actual parts mountings, such as those for the engine mounts, are somewhat 'weak' in some areas. I made my own brake lines, and had to adapt some mounting points. Also, the rubbery tyres don't fit well on the rims, and had to have a bead of PVA run around them to seal them and stop them wobbling about.
That said, once done and painted, it looks very good indeed.
I have a build review written for a magazine article a few years back, (whcih I tried to send to Bill, but couldn't get it to 'go' to his e-mail address). You're welcome to a copy, although I only have my 'reject' photos left, as the originals went to the magazine. (the article was shelved due to a 'breaking news' feature, and then the interest had passed, so it wasn't published).
Sorry to interupt your thread, but thought I'd answer the question.