I, too, am having some difficulty with the numbers given in the climb
comparison.  If the rate of climb went up from 1250 fpm to 2000 fpm that
indicates a 62.5% increase in climb performance.
The excess horsepower needed to improve the rate of climb this much cannot
come from a few percentage points increase in prop efficiency.  I smell a
testing flaw here.
Walter Dodson  IV-P  in flight test