It only makes sense to drill off the inferred to a higher category if the inferred resource is at the shallower depths. Otherwise it would be waay to costly (if I remember correctly up to $1,000,000 for the deeper holes), and most here recall the technical difficulties that were encountered hitting the ore body at those greater depths . Presumably they would likely only prove up the deeper resource via underground drilling once mining was well-established...non? Perhaps sending out a scout drill to some of the more prospective regional anomalies would be the better option....poke some holes down to 500m?...

Cheers, Luker