The rally's opening two stages today will be run in the dark, on forest roads west of Rangiora.
"We've just finished working on the car and are ready to go," said Mason. "Quite a bit will depend on the weather this weekend, especially through the night stages if it gets really cold.
"Since we're the championship leaders we get the choice of starting anywhere in the top five, so we'll wait and see what the weather is going to do.
"You don't want to be driving night stages if there's a lot of dust around so I'm pretty sure we'll be starting number one.
"We're confident this weekend as we've managed to get a pretty good points lead on everyone and we've got some momentum going now.
"All the rounds from now on carry fewer points than the opening two, so it's handy to have a healthy lead for the rest of the championship."
Summerfield is determined to make the most of his hometown advantage and try to catch up on Mason. He showed good pace and consistency in the opening rounds, and wants to put on a good show for the local support.
"We're going to have to go for it as Richard [Mason] is flying and in a league of his own," said Summerfield. "If there's any time for us to try to catch him, it's this weekend with home advantage, which I want to make the most of.
"We'll have a good go and see how we go. We've made our package a little bit more reliable, as it let us down a bit at the last rally."
Another local Canterbury driver, Matt Jansen, impressed by coming third overall in round two at Dunedin on his return to the championship.
Jansen is a former national junior champion and he and Summerfield know the Canterbury stages and conditions well enough to challenge Mason's dominance.
Third in the championship is 19-year-old Lance Williams who is doing a fine job in his rookie championship season.
Another in-form youngster is David Holder, who had his first podium finish in the last event at Rally Otago, coming second in his ex-Hayden Paddon Mitsubishi Lancer Evo.
Holder, who is being mentored by WRC driver Paddon, has shown great speed since moving to the four-wheel- drive class.
Emma Gilmour continues to develop her new Suzuki Swift, and while she's not a championship contender, she was running second to Mason at Rally Otago until the engine let go.
"I want to just continue on from Otago and keep improving the car's handling and pace, so I can challenge Richard's stage times," said Gilmour.
She's looking forward to the longer stages on farm roads near Cheviot tomorrow, where she will be able to give the car its head.
Missing from the start list will be last year's Rally Canterbury winner, Chris West, whose high-speed roll badly damaged his Mitsubishi. With only three weeks between events the team have been unable to complete repairs.
The ceremonial start is from the Palms Shopping Mall in Shirley this afternoon. Crews then go to the Okuku Forest, west of Rangiora, for the two night stages.
Tomorrow's competition goes as far north as Cheviot in a further six stages.
