But Rees still quickly found himself among the leading trio of riders.
Tom Toparis, from Goulburn in New South Wales, was out in front, while Rees and Newcastle's Max Croker battled hard for the runner-up spot.
Rees made a determined effort over the final few laps to get on terms with Croker and made his move on the last lap. He made his first thrust at Hayshed corner, then sat on the tail of Croker at MG Hairpin but couldn't quite get there on the run to the line and Croker managed to hang on to that second position.
"I'm pretty pleased with that," Rees says.
"I started off the season with a stock engine and was three seconds a lap off the pace of the leading guys. But I progressed through the season and at the end I was going 1.8s a lap quicker at Phillip Island than I was at the start of the year. That's amazing progress.
"I was always there or thereabouts for a podium finish, but a DNF when I crashed at the previous round at Winton cost me dearly ... certainly cost me a podium finish for the championship. But that's racing I suppose.
"Even so, I finished the year in Australia strong and I'm happy with that."
Rees said he was now looking forward to racing both a Honda CBR600R and a Honda CBR1000SP1 in the upcoming Suzuki Series pre-nationals competition in New Zealand, contesting both the Formula Two (600cc) and Formula One classes.
He will then tackle the four-round New Zealand Superbike Championships, starting in Christchurch on January 5-6, racing in the Superbike class only.
Australian Supersport 600 Championship final round result
1st Damon Rees – 36
2nd Callum Spriggs – 35
3rd Max Croker – 33
4th Scott Nicholson – 33
5th Nic Liminton – 31
Australian Supersport 600 Championship standings for 2018
1st Cru Halliday – 361
2nd Tom Toparis – 308
3rd Max Croker – 246
4th Damon Rees (New Zealand, Honda) – 231
5th Zack Johnson – 204