Annoyed to have conceded any points given they had the breeze, Wanganui replied right before halftime with Rawiri smashing through a gap and feeding Nabuliwaqa for his second.
Rawiri took over the goal kicking from the accurate Grayson Tihema and would also have the tougher prospect of trying to convert into the near gale during the second half.
Horowhenua Kapiti initially made good use of the wind at the turnaround with first-five Aaron Taiapa landing an early penalty, while Wanganui had to keep ball in hand and made a few risky passes.
Some good defence and ball recovery from prop Vaan Rauhina and Tremaine Gilbert made sure the home side stayed out of their danger zone, then Lama scooped up a bad Horowhenua Kapiti fumble and fed halfback Kane Tamou, who showed his deceptive pace to outstrip the chasers in a 70m dash to the line.
Horowhenua Kapiti reserve forward Seaton Kuru pulled it back to 36-13 with a barge over try.
Tempers flared with Wanganui back on attack as a brief pull-apart fight saw both teams get a warning from the official, but visiting prop Kenneth Macaulay didn't get the message as on the very next phase he caught Ulukuta high, receiving a yellow card after reserve loose forward Kieran Hussey had dived low following a series of rucks at the line.
Rawiri would cut loose to score Wanganui's last try, running under the posts to give himself the opportunity to convert into the wind.
The RDO Shield final win wraps up another good campaign for the Wanganui seconds, who beat Wellington Maori Colts 79-19 at Cooks Gardens, beat Horowhenua Kapiti Development 24-10 in Otaki, and draw with Wairarapa Bush B 23-23 in Masterton to make the playoff. It was also two titles in a row for coach Shane Ratima.
In other results, the Wanganui Under 16's had a 24-10 win over Horowhenua-Kapiti at Spriggens Park.
Wanganui Development 48 (M Nabuliwaqa 2, T Rawiri 2, A Lama, K Tamou, K Hussey tries; G Tihema pen, 3 con, Rawiri 2 con) beat Horowhenua-Kapiti Development 13 (J Hynds, S Kuru tries; A Taiapa pen). HT: 31-5.