Ann: Mining of First Ore Block at Granville Tin Project, page-262

Not trying to contradict but from memory the terminology used by PW is that payment is ex mine gate , doesn't of course make a whole lot of difference but i've seen a few people quoting different payment schedules but i'm pretty sure that was the way it was explained.
I agree with the "building inventory" theory , makes sense and it would be something that most of us would do ourselves ( kinda like our shareholdings ) hold off until you think it peaked OR until it starts to slip back a little. Time will tell and so will the ANNs (whenever they come ).