Hurricanes flyhalf Cruden had opened the scoring with a third-minute penalty and while both sides had opportunities to score more points, their defensive lines held out.
Smith scored the only try of the game in the 36th minute after scrumhalf Jimmy Cowan spotted there were no Hurricanes defenders behind a ruck, so he popped a delicate chip kick into space near the line, which the fullback brilliantly regathered and dived over.
Sopoaga added the conversion and then a penalty right on halftime to give the Highlanders a 10-3 lead at the break.
The flyhalf extended the lead to 10 points with his second penalty just after the break, though Cruden reduced that deficit shortly after with his second penalty.
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