Karl, I think I have some accurate info on all the Spits Johnson used carrying the different forms of JE-J codes, including the two MkIX's, one of which was used as his 'back up' machine. I'll see what I can find in the 'rubbish plie' of as yet un-filed paper etc! However, if you're doing it OOB, you proabably won't need it!
As I mentioned on the 'phone, here's a quick answer to any problem areas with the kit.
Although I haven't yet built my example, I've done numerous test fittings and 'what if...' studies, and reached the following conclusions.
1) There is a certain amount of flash present, but nothing which can't easily be removed.
2) I only found a couple of sink marks, which are easily rectified, unlike the early examples of this kit, which had them all over, including the wheels. Also, there is no evidence of part-moulded components on my example.
3) The mould release agent used here is very heavy, meaning the parts must be washed before construction begins. It's too heavy to allow it to be removed by normal handling during construction.
4) The lack of locating pins means it's a good idea to cement small 'tabs' of plastic card into areas along one fuselage half, to aid in joining the fuselage. Careful alignment and taping in place is required to ensure a smooth joint.
5) Examination/test fitting suggests the model can be assembled without including the engine assembly, although the engine bulkhead might help in alignment and strength. The cowlings are moulded as part of the fuselage (with secondary, separate cowling parts too), with recessed 'cut' lines moulded in. Exercise care when aligning the nose area, and there shouldn't be a probelem, although you may need to fit a spline to hold the prop in place.
6) One area criticised in some reviews is the shape of the control column grip, which has been described as 'square' On my example, it's more oval, and not that far different from the later grip with the cannon trigger. To be honest, once painted, it will hardly be noticed, so it can be left as is.
7) Other than the above, this is probably the best kit of the MkIX, certainly in 1/48th scale, with the possible exception of the new Tamiya 32nd scale example, which isn't really a fair comparison, and, given careful handling and accurate alignment throughout construction, shouldn't present any major problems.
Hope this helps mate, and looking forward to seeing it develop.