Thats why Neils creation is consider to be a full scale machine of its own and not a model of anything .Specially when not representing a cockpit area .
So maybe Guinness should give Neil the title of "Fastest remote-controlled jet-powered aircraft" and remove the word "model" .
It is a model because that is what he said it was. Just like a Giant Ugly Stik or the rubber powered stick planes you built as a kid. If you can imagine that it could be a real aircraft then you can call it a model of that imaginary plane. If you create something you can call it whatever you want.