We do not know how tall Kenny is, but comparing him with the length of a single blade suggests to me that it is longer than 1270mm.
Henry mate as an artist I think I should point out something to ya mate.
It even affects pilots in VFR...
A little matter called perspective.
That's how you can tell the difference between a fly on the windscreen and approaching traffic.
This Kenny fellah is standing a good 12 feet back from the props so the props seem bigger.
RNZAF did operate Vickers Wilderbeasts in the early war so they may be blades from those... just a hunch.