Nice challenge, I never knew that the F-25 had controls on one side only.
Originally Posted by
oncemorealoft
the
Difoga 421 aircraft, home-built and -designed secretly during World War II
This is the popular story, but it is incorrect unfortunately. It was built using available materials only, but there was nothing secret about it. A model was tested in the NLR windtunnel in Amsterdam and the report about this was published. The company applied for both a registration and a certificate of airworthiness through the normal channels in 1942. Due to 'the current circumstances' this could not be accommodated, and because of this the application as well as the already paid costs were returned. The purpose of designing and building the aircraft was purely commercial.
In Dutch only, but see here for the evidence (includes a lot of photos of the aircraft as well):
https://www.hdekker.info/DIVERSEN/Difoga%20421.htm