To add to the discussion, the lead article in the latest issue of Air Power History magaine (Summer '09), pub'd by the [US] Air Force Historical Foundation, has an article that might be of interest: "Racing Against Invasion: Engineering a Kamikaze 'Cruise Missile'," by Thomas Momiyama; he makes some good use of reference materials in Japanese, and he lays out some of the background on the MXY7 machines in the Smithsonian Air & Space Museum's collection.