While building the Unicraft FTB conversion (in 1/72), I found certain things didn't jive with what info was available. So as I'm an Air-Britain member, I was able to ask the Rolls Royce specialist who just happens to be David Birch (he's also the official Rolls Royce Historian) about some things. He was able to confirm what the overall length was as the 1/10 wind tunnel model still exists and he knew who has it. Another bit of info he gave me was that the wind tunnel tests showed that the tail surfaces were undersize and needed about 60% more area. He then told me that the plan was, if the project had proceeded to production status, the aircraft would have had a Tempest tail assemble (a complete Tempest tail assembly was issued to RR for the project). He said that he didn't know of any model of it with the Tempest tail.
But now he does know, 'cause I built one and then sent him the photos of it. He said he was quite impressed with the result.
Top pic is of the PV Fighter (Private Venture), middle photo is of the FTB Tempest tailed version, I also have it as testing the RR Crecy engine, then the bottom photo of the two together.