Well, it seems that Bill and Xanadu are not the only ones building a really big Spitfire model. See what you can get yourself into if you keep scaling these things up!
These are from a FULL SIZED, flyable Spitfire under construction. Of course it was not scaled up from the Guillow's plans, but it's not far off the mark. They are building it of wood with balsa and birch sandwich skins, the same construction method as the Mosquito. In a way, it's not too different from what Xanadu is doing with the Depron foam. It will be powered by an 1100 horsepower, Allison V-1710, more available and cheaper than a Merlin, and since it is expected to be over a ton lighter than an original Spitfire, is expected to have equal or better performance. The objective is to have a Spitfire to fly that does not cost millions of dollars a year to maintain in flyable condition as a real WW2 Spitfire does.
If you are interested in more details the web page is at:
http://www.spitfireaircraftco.com/
The kit is only $320,000.