In round three Wellington defeated Bay of Plenty 31-10 in Rotorua with three All Blacks in the pack who crucially are missing from tonight's game.
Mewett says fronting up physically is the key factor against Wellington.
"When we played these guys we managed to hold out up front for a while but it can be pretty fatiguing if you are not switched on to every phase in the game. I think we have matured in that way and I think we will be able to hold that out for 80 minutes this time."
It may have surprised some pundits that the Steamers have gone all the way to the final but not the players. It was a clear goal from the outset, Mewett says.
"As a team we had pretty high aspirations for the season with the squad that we had so it is not too far-fetched to say I was hoping for this, but the way it has come about was not the way we wanted it.
"It has been a pretty rocky sort of road to get here. These last three games have been excellent. The boys have really turned up, have listened to the detail we have put out on the field from the coaches and it is definitely working out.
"We are sticking to our plans and our systems and having that momentum going into this final is priceless."
Mewett grew up in Australia and came to New Zealand as a teenager. He always cherished one day wearing the Maori All Blacks jersey.
"From an individual point of view it is definitely the proudest moment in my rugby career. I am 30 now and didn't expect anything like this to come up. It has always been a goal of mine," he said.
"When my name was read out at that press conference it was pretty surreal and it is only just starting to sink in now."
Steamers hooker Polwart represented New Zealand under-20s in 2015 and follows his older brother Sean into the Maori All Blacks, to the delight of his close-knit family in Thames Valley.
"I was over the moon and rang my old man, and got calls from my family. Everyone is really proud and I am really proud. I can't wait to pull the black jersey on again."
