Seemingly the only current Drover driver around at the moment, a few comments might be appropriate?
1. Ozaggie's surmise is probably correct, but not with me driving, thanks.
2. Having had 2 "precautionary shutdowns", she flies ok on 2 engines. Better if it's the centre engine failed as there's no drag from the rudder [85kt cruise{?}], but sits at 80kt with the centre and an outboard going.
3. It is NOT 3 Tiger Moths in close formation, but Chipmunks! The engine is the DH Gipsy Major 10 Mk2. Having refamiled the aerodynamicist and production manager with the olde girl, they had wanted to put American engines on her, but post-war cashflow [NOT] and British heritage won the day.
4. From the gent who was the Flight Test Engineer looking over Black Jack's shoulder, the DH variable pitch [two position; Fine/Coarse] prop was ok until it shed the odd blade causing two crashes. Not due to the engine failure but cutting through the side of the cockpit and disabling the pilot!!
5. Probably the most illuminating fact from the aerodynamicist [and these guys took some convincing to go for a quick circuit!
] was when he asked how she flew as she's unstable.
I'd sorta worked this out, but I asked how Black Jack determined stability [given that FAR certification was a long way off in 1948!] and suggested maybe trim out and count to 10. "Yep, that's about right" was the answer.
So, there's some food for thought.
G'day
PS The reason she didn't go so well with the Lycomings was the added 2,000lb of takeoff weight!!