I agree with your CAS for the DA40D at VS0 of 54kt (at 1150kg), but I make it 57kt for the NG. (As its graph of IAS vs CAS starts at 65kt, I've assumed the same +1kt discrepancy at 58kt, which is its VS0 at the same mass.)
Also, as the basic mass of the NG includes an extra 50kg for the engine, plus beefing up of the undercarriage to support it, the takeoff mass is going to be greater for any given load, hence VS0 will be even higher.
So, not quite a wrap.