Ann: Drilling Confirms High-Grade Main Feeder at Liontown, page-193

"That means 520tpa ore feed at 12.5% Zn, which is a fair rate of development and extraction for a deposit spread out over 1.5km and 400m depth."

I would have thought it an advantage to be spread out over 1.5Kms as takes 8 times as many linear meters to go vertical with a decline compared with a drive going horizontal plus can work on several stopes at the same time ie belleview gold project
On your 5.75 LOM and 400M depth that is 70 meters a year of extraction depth annually seems pretty standard , maybe more an issue about the number of parallel lodes to get the tonnage which infers relatively narrow veins compared with say a single ore body for the same tonnage per vertical meter so more cross cuts large enough to take TBJs and LHDs for tramming , , higher dilution into reserve if objective is to get valid reconciliation on the ROM pad rather than to get financing . .

I do not know the logistics in carting ore ore from Lion to toll float , or ore sorting of their ore , but SHN maybe could be considered a bolt on for another company your "satellite mine ") , rather than an "exploration company"
For me really would need the observations of a mining engineer to get any sort of validity on what is a valid cut off grade . and then work up from that to get a reserve .