Yes they can "technically" mine down to under 1 metre widths,...

Yes they can "technically" mine down to under 1 metre widths, but thats a different type of mining methid from cut and fill (take the ore out and return the gangue and then set up on the gangue and mine out higher up the seem.) to do that they will need at least 1.5 metres I think for access and egress of the ore.
Cut and fill would seem the best method on a near vertical seam.


To do it under 1 metre they still need a development drive on one side of the stope possibly two sides to work from then make long horizontal holes (shaped to explode in a manner that a narrow 1 metre horizontal slot will be removed)load them with expolosive fire it and then use a scraper system to remove the ore after drilling I guess that is some type of long hole stoping method.
That method would be more appropraite I feel if the ore body was a horizontal lens (looking like a swimming pool in form and view, rather than being almost vertical as you imply.
Instead the ore body is basicly still the shape and width of a swimming pool (100 metres long 1 metres deep) but the "pool" is flipped up on its side at a 30 degree lean from the vertical, and "down dipping".
I am not a geo or a miner so prepare to be refuted but thats how I see it from my amateur perspective.
As you imply the development drive while not technically mining will cause dilution.

Really if HEG wants to get ahead they need to somehow increase production considerably now they have proven they have the ore.