There were several thing's which I had a hard time explaining. Firstly, this was in 1947, not 2005. The information this person seems to have makes it hard to discount, where would he have gotten this kind of info? I doubt one could even make it up, without some kind of first-hand knowlege of flying-saucer's. They did'nt have the internet, all they had was radio.
More importantly, if he HAD no first hand knowlege of this, then why would the FBI even posses it? Interestingly, toward the end the writer goes in-depth into the armament of the craft, and it's different compartments. Why the hell would he do that if he'd never seen one?
He suggest's that these craft's or craft (that he studied) could go from one plane of existance to another. Furthermore, even if the guy WAS doing research with recovered flying saucers that does not mean they would believe him. A lot of his theories are just that, but theories born of study and first-hand knowlege in my opinion.