Drill spacing is often evaluated from a resource estimation and grade continuity perspective, with geologists advocating for tighter spacing to improve model accuracy. However, the cost of increased drilling should be considered with the tangible value addition, particularly the positive impact on revenue. At Northern Star Resources Ltd’s South Kalgoorlie Operations, gold mineralisation is adjacent to a weak ultramafic unit in the footwall. This ultramafic is highly susceptible to overbreak, and in some cases has led to complete sterilisation of longhole stopes before ore is extracted. Understanding the ultramafics location is key to stope performance. This study assesses the impact of increasing grade control density from 20 m × 20 m to 10 m × 10 m. The aim is to improve orebody definition, refine the lithological model of the ultramafic, and enhance stope design, ultimately reducing dilution and offsetting the additional grade control drilling cost. Current grade control drilling (20 m × 20 m) is conducted prior to the establishment of ore drives. Ore drives designed on this drill spacing aim to avoid intersecting the ultramafic contact while following the strike of the orebody. Although geological direction and mapping are used to refine drive and stope positioning, the contact is visually subtle and undulating resulting inconsistent mapping and subsequent re-development. Exposure of the ultramafic, either through development or longhole drilling of the above stopes, can lead to significant dilution, impacting the economics of mined stopes. While engineering controls have assisted, the most effective mitigation is avoiding exposure of the ultramafic altogether. Tighter grade control spacing (10 m × 10 m) aims to better define the ultramafic contact while also increasing confidence in grade distribution. This enabled more precise drive and stope placement, optimised pillar design, and reduced geological risk during ore extraction. Where stoping followed the plan, observed dilution was reduced to 11 per cent from 26 per cent in comparably mined areas. This demonstrates that the additional cost of drilling is outweighed by improved mining execution and reduced dilution.