We have seen what may be a gradual development of the central figure - a tree growing from a nut - into what looks like a canoe taking shape from the trunk (Ca1-19), and now, (in Saturday, the darkest time of the week) how a canoe may be ready for launching:
hua poporo Ca1-19 Hb9-54

Possibly, what is illustrated is a growing solar tree (miro tupu) symbolizing how light grows, how it reaches its maximum height and then is felled. From the trunk a canoe (miro) can be shaped, to be launched at new 'year':

Miro

1. Wood, stick; also (probably improperly) used for 'tree': miro tahiti, a tree from Tahiti (Melia azedarach); miro huru iti, shrub. 2. Wooden vessel (canoe, boat); today pahú (a Tahitian word) is more used, especially when speaking of modern boats. 3. Name of the tribe, of royal blood, descended from Ariki Hotu Matu'a. Vanaga.

Miro-oone, model boat made of earth in which the 'boat festivals' used to be celebrated. Vanaga. ... on the first day of the year the natives dress in navy uniforms and performs exercises which imitate the maneuvers of ships' crews ... Métraux.

Tree, plant, wood, plank, ship, building; miro hokuhoku, bush, thicket; miro takataka, bush; miro tupu, tree; miro vavau, switch. Miroahi, firebrand. Mimiro, compass, to roll one over another, to turn in a circle. P Pau.: miro, to rope. Churchill.

1. Wood. 2. Ship (Ko te rua o te raa i tu'i ai te miro ki Rikitea tupuaki ki Magareva = On the second day the boat arrived at Rikitea which is close to Mangareva. He patu mai i te puaka mo ma'u ki ruga ki te miro = They corralled the cattle in order to carry them on to the boat.) Krupa.

T. 1. The tree Thespesia populnea. ... a fine tree with bright-green heart-shaped leaves and a yellow flower resembling that of the fau, but not opening wide. The fruit is hemispherical and about twice the size of a walnut, consisting of brittle shell in which are several septa, each containing a single seed. The wood resembles rosewood and is of much the same texture. Formerly, this tree was held sacred. Henry. 2. Rock. (To'a-te-miro = Long-standing-rock.) Henry.

(Thespesia populnea, Wikipedia)