Unfortunately, although finding out what the modifications (or most of them) were is fairly straightforward, finding out why is a whole different ball-game. For instance, the Paddy Finucane story came from an (alleged) eye-witness, but, in a book that I recently read, the author said that he simply disobeyed instructions (to always abandon by parachute, and never ditch,) and the Spitfire flipped over onto its back, trapping him inside, and dragging him down.
While it's gratifying to have praise heaped upon my head, over my knowledge about Spitfires, it is, in fact, largely recent, from reading files in Hendon and Kew. There is a bit of a down side to it, though, since I often have to ruin someone's cherished beliefs, and that has been known to cause some acrimony. As an example, and this will bring a "smart-alec" response, I was taken to task, years ago, for using "marque" when referring to aircraft; "Cars have marques," I was told, "Aircraft have Marks." Sorry, Steve.
Edgar