Ionlybuystinkers (I like the name); if I use 10%, my NPV drops...

Ionlybuystinkers (I like the name); if I use 10%, my NPV drops to $248mill.

I think 10% is too conservative considering how low inflation is and the way interest rates are falling and likely to fall further. Discount rates are about opportunity costs.
Cash in the bank might get you up to 5% and that's likely to fall this year.
A 5% discount is more appropriate.

However even this may be too conservative in my model because I assumed a flat gold price.
Most of us that invest in gold stocks do so because we expect gold to continue to trend higher.
It's been trending up over the very long term and its been trending up steadily for the last 10 years.
I see nothing about the state of the world to suggest it won't keep trending up.
If it does, the rising gold price and stronger resulting cashflows in later years should offset the need to discount at all.

However the point of my estimate was to try and determine what NPV the scoping study would come up with and I expect they will probably use a 5% rate and flat gold price.
They may assume a lower than spot gold price though.