Derek Sheils followed up his Enkalon Trophy success at Bishopscourt on Saturday by winning the feature Mayor's Trophy race at Kirkistown on Monday.
The Dubliner came home ahead of Jamie Hamilton, with Alistair Kirk third and Stephen Thompson in fourth.
Kawasaki rider Sheils was in the running for victory in Superbike race one, but crashed out unhurt at the last chicane, Hamilton taking the win.
Thompson and Kirk completed the podium places on a sun-kissed afternoon.
Cookstown B.E. Racing rider Hamilton won the first Supertwins event from runner-up Christian Elkin, with the former British 125cc champion turning the tables on the Ballyclare rider in race two.
Robert English won Supersport 600cc race one after William Dunlop, a double winner at Bishopscourt, crashed out without injury.
CD Racing Yamaha rider Dunlop recovered to take victory in race two, with English coming home second.