I know no more than is in that article there, but have to question whether a 1000hp, 6+ seat composite turboprop is really suited to amateur construction (and presumably also lack of independent oversight of the design standards).
There's a reason most countries insist on anything above a certain size - usually 2 or 4 seats and around 240hp, going through a deep and formal approval process, and that is basically down to the number of lives that can be lost.
G