Blast from the Past ! (but Johnnie-Come-Lately has only just spotted this Thread - usual playground "Military Aviation">"Gaining an RAF Pilot's Brevet in WWII").
The B word (your #1),
...the narrow track undercarriage that was always a handful...
Not on the real thing ! Did 75 hrs in summer '42 on Mks.I and II at OTU, sent to India (where there were no Spitfires then), went back in after war in '49, flew 300 hrs Mk.XVI (20 Sqn) and a few on XIVs and 22s.
The general rule was/is (on tail-draggers): wide track, good - narrow track, watch it !. The Harvard (which we'd nearly all come from) would do a graceful pirouette at the drop of a hat. But the Spit had beautiful manners (on ground and in air), never heard of anyone (inadvertently) ground-looping.
...PS. yes, I know Mrs Grace lost her husband and she finished his Spitfire and now flies it in his memory. But does that excuse her opinion in the letter?...
I think so. Her point is valid, maybe firmly expressed, but still good.
There have never been any full size Spitfire replicas
AFAIK (what would you use to replace a Merlin ?), plenty of full sized plastic fakes as gate guardians, of course. And a variety of nice downsized flying models of Spits (wasn't there one a few years ago that used a Jaguar 5300 V-12 ?), but that's all they are, whether or no you can shoehorn a man into them (there wasn't much spare room in the real thing, come to think of it).
That leaves the Mk.IX(T). Apart from supplying the 20 (?) Mk.IXs for the conversion, the RAF (wisely) had nothing further to do with them. Any military pilot of wings standard could jump in a Spit and fly it away (as thousands of us did). ♫....Why was it born at all ?..♫
I think the buyers, Irish, Indian, Belgian (any more ?), who were rebuilding their Air Forces post war, saw them as a cheaper (sterling) altenative to the second-hand Harvards (needing dollars). They were buying bargain basement late model Spits anyway, these should be the ideal advanced trainer for them. The Grace Spitfire, is, of course, one of these hand-me-downs.
Except that it didn't work (note that the BBMF has chosen as a lead-in for their new boys, not one of these, but - a Harvard !)
Will have a good long read through this interesting Thread and put oar in from time to time, if I may, and if Moderator will have me.
Danny42C.