No, in the old days the d shaped sound hole was for rhythm guitars. Think sound waves here. If you have a great gaping hole the sound will escape quicker. If you have a small hole the sound will reverberate more and then leave through a small hole. These days it doesn't matter as they are all miked up or have a pick up in them!
As for bireli, I was being polite. As a Jazz guitarist myself, it is etiquete (I have found) that you say the pupil has equalled the master, especially when the master is dead. As for Niculescu, however, I will say that in my opinion he is much better than Grapelli.
Oh, Babik ( Django's son) favoured the Gibson es-175 as did most of his hot club of france.
Enjoy the style it is truelly undervalued and underplayed. (That is the style i play.)