Rees' two series victories pushed him up to second in the Suzuki F1 Superbike championship, behind Frost.
Saiger was third in the title chase followed by Moir and, equal on 74 points, Jamie Maindonald and Andrew Stroud, who didn't race at Whanganui.
The Robert Holden Memorial finishing order was Rees, Saiger, Summers, Perth-based Adam Chambers riding his smaller capacity Wolfpack Racing Honda CBR600RR, and Swiss Red Devil Racing Kawasaki ZX-6R rider Roman Stamm, returning after injury at Manfeild.
UK-based Tim Reeves again easily won the Quality Inn F1 Sidecar races on the Carl Cox Motorsport E-Aide LCR with new passenger Robbie Shorter, although the pairing of Aaron Lovell (Hamilton) and Tracey Bryan (Tauranga) had qualified their Shuzi LCR on pole.
In race one, the Auckland-based Adam Unsworth/Stu Dawe combination shot their Eni Windle F1 off the second row of the grid ahead of Lovell, but behind Reeves. The positions didn't change all race, with Masterton's Spike Taylor and Astrid Hartnell fourth on their Stealth Electric Bikes LCR.
Reeves cleared out to win race two by nine seconds from Lovell, followed by Unsworth, Winter and Taylor.
Therefore the seven-time world sidecar champion Reeves won the 2015 Quality Inn F1 Sidecar title ahead of Lovell/Bryan, Unsworth/Dawe and Taylor/Hartnell.
Aucklander Daniel Mettam won the Nationwide Accessories F2 600 Suzuki Series on his RCM Suzuki NZ GSXR600 after series leader Shane Richardson (Wellington) crashed his Motorad Kawasaki ZX-6R while entering turn one of the opening F2 race which he was leading.
Tony Rees' 20-year-old son Damon Rees finished overall second on his Honda Rider Insurance CBR600RR in the F2 series, just 1.5 points ahead of fellow 20-year-old Richardson, then Adam Chambers and Roman Stamm of Switzerland.
With Richardson out of the opening race, Mettam went on to win from Stamm, Rees, Isle of Man rider Billy Redmayne on his Biggles Racing ZX-6R, and Shaun Harris (New Plymouth) on his TT1 The Chassis Shack GSXR600.
While Chambers could muster only seventh in race one, he snatched a brilliant victory in race two to win by just 0.089 of a second from Richardson (Wellington), who made a fine recovery after his earlier fall. Mettam rode a safe third with Harris improving for fourth, and Stamm fifth.
Other 2015 Suzuki Series class winners are John Oliver in BEARS senior, Robert Whittall in BEARS junior, Eddie Kattenberg in Post Classic senior, Shayne Lawrey in Post Classic junior, Gavin Veltmeyer in F3, and Duncan Hart in Supermoto.