Funny - it's been a long while since I ran my VA Mk1. I have two and have never flown either.. (loser). I recall when I first ran up the one on the bench, with large venturi and 15% fuel and bladder pressure on a clipped 5.5x2 (around 4.75 or 5x2 IIRC). it wailed, and it pulled harder than I ever felt a TD do. I did not have a tach at the time, but I seriously doubt a TD would have come close to it. Yet I see comments that they aren't much different than a TD. As you suggest, that must be people running them on 6x2 props and the like. As far as I know let them spin and they will indeed leave a TD behind.
I wonder how the Cox .05 carb would do on a Mk1? I forget if someone has done that yet or not.
The 5.5-2 is a lighter load that one would compare to a typical 'go-fast' prop for the TD. They were ported and timed to make power at lower rpm that made props like the 5-3 square tip viable. Prop choices were much more limited for most of the TD's life, unless you were a serious CL flyer and then you either cut down or molded your own props.