The race route follows the DOC track from Kerr Bay car park (at Lake Rotoiti) up to the top of the St Arnaud range.
The race start is ~1km from the car park, along the St Arnaud Range Track. It is not marked (DOC took down our sign, fair enough) but starts immediately after you cross the creek bed at the junction with the Loop Track:
https://www.topomap.co.nz/NZTopoMap?v=2&ll=-41.811718,172.861613&z=15&pin=1&lbl=Vertical%20K%20start
https://goo.gl/maps/Wci6wu5Cts52
The first 700m of ascent is up through beech forest on a rough but well marked track. The final 300m of ascent is a scramble up loose scree (above the bush line) to the top of the ridge. The route up the scree is sparsely marked and you’re free to pick your line.
At the end of the race, you’ll have to make your way back down the same track to the car park.
Strava segment: https://www.strava.com/segments/17064545