The Australian Institute of Sport / NSW Institute of Sport racer is coming into some strong last minute form by stringing together solid results in the last two events.
The race down the 904-metre course in 7.2 degree foggy and rainy conditions saw Canadian Tristan Tafel take first place, with American John Teller in second and Canadian Christopher Delbosco in third.
After qualifying in 21st position to reach the finals, Grimus came up against the event winner in the first final and crossed the line ahead of the Tafel to record a confidence boosting victory.
However, in the next final, which included Tafel once more, fortunes failed to favour the young Aussie, with Grimus not finishing due to a crash.
AIS ski cross program head coach Matt Lyons said that he was pleased to see some encouraging signs from Grimus.
Lyons and Grimus have been focusing on a number of technical factors that are now starting to pay dividends.
Teammate Sami Kennedy-Sim finished in 12th place overall after she was pinched out on one of the turns in her quarter final, forcing the Perisher athlete into third place, resulting in her missing a semi-final berth.
The final was won by Austrian Andrea Limbacher, ahead of David and compatriot Alizee Baron in third place.
Katya Crema unfortunately did not qualify for the finals, finishing in 18th place.
The three AIS / NSWIS scholarship athletes will now regroup and do it all again in the second stage of the double header tomorrow.