Yes BnZs. To isolate energy retention from thrust I timed a power off glide, prop feathered on all aircraft (twin engine aircraft feather automatically). I know you're not in love with this method, but aircraft that score poorly in Eg Retention but which still seem to hold energy well are well represented in categories like level acceleration and climb rate.
The point is the Hurricane and A6M are some of the worst diving aircraft in the game, but the Hurricane rolls ok at speed so that makes it seem to dive better than it really does. People complain about Hurri IIC's that catch them in a dive, and I just shake my head, because if a Hurri IIC catches you in a dive it simply means you really screwed up.