ADN valuation - what DFS NPV is required to justify a SP increase from here?

I don’t hold any ADN, but I do have a lot of MEP, which is undervalued by about 60% relative to ADN, assuming the full value of MEP’s 25% share can be realised for (long-suffering) shareholders. So I’m keen to understand the potential of ADN.

The Andromeda Pre-Feasibility Study announced 1 June 2020 had the following parameters:

• After-tax NPV8%: A$511m
• After-tax IRR: 135%;
• Maximum cash requirement: $28m
• Payback period: 15 months (from start of mining)

ADN Market cap (based on 2,248m shares & options):

• After feasibility announcement (5.9c close on 1 July): $134m = 26% of NPV8
• Current (24c close on 3 Dec): $540m = 106% of NPV8
• Peak (33.5c close on 23 Oct): $753m = 128% of NPV8

A quick review of other companies after-tax NPV and EV shows that typically NPV is 35 to 70% of EV - let's say 50% as an average. So at the current 24c price and the 50% ratio, Andromeda is pricing in a post-tax NPV of around $1.08bn from the Definitive Feasibility Study that we expect in the next six weeks or so.

Questions for punters:

• Is a 50% NPV:EV ratio reasonable for Andromeda?
• Is a post-tax NPV from the DFS of at least $1.08bn likely?
• Other thoughts on valuation?