In one five-minute spell, Sycamore dived bravely at the feet of a United striker to foil an attack and then tipped a rasping shot on to the post.
Both keepers commanded their penalty area and dealt confidently with the high ball into the goalmouth.
United struck again at a crucial stage, in the 62nd minute, with a goal to Rubi Perano from the penalty spot after a United attacker was brought down in the penalty area.
Riverina fought back, with midfielders Dara Mulrooney, Tori Lolohea and Manaia Mill, and striker Lizzie Hall all prominent.
But they could not breach the tight-marking United defence. Rubi Perano was outstanding in a solid, hard-working unit.
United’s midfield also came to the party on defence. Veteran Karen McDonald played a central defensive role, and left the forward runs to the mobile Kayley Knight and Jamie Gedye.
The match was played in good spirit, which helped referee Chris Niven and his two assistants keep everything in order.