Iain,
Looks pretty good. The exhaust rust is maybe a tad too orange for some, but I think it looks quite good. I like the missing storage bin, too.
I do not remember if they were the same or not on the real Panthers, but your tracks are not matching in their directions of run (look at the angled ice cleat ridges on the edges and the hinge joints).
Unfortunately, it looks like their is a gap between the rear hull plate and the left side sponson plate at their joint. Not sure how you can fix that other than the old trick of caking on some mud and grime to cover it.