My rv9a matches these number fairly well, but only after the upper and lower intersection fairings were installed. And it is amazing how much those teo pieces helped.
But I will never get the Vans range. It seems the range was calculated with no reserves and just based on simple math of fuel qty and fuel burn. I dont fly that way; I like to keep a min of 3 gal in each take in addition to the 45 min FAA reserve. Thus cuts down my effective range considerably. So my usable fuel each flight is no more than 24 gal. This still gets me really far at 55% power (4 hours), dont get me wrong. JMHO
Your mileage may vary ( pun intended)