Possibly tupu te rakau would have been more useful for understanding what GD88 means. But such a label would have been too long for comfort. So it became hura, and Metoro said so at least a few times when he saw a sign with 2 of these connected 'balls'.

My prototype for hura has 4 'balls' in a crosswise configuration, and such is also the arrangement of hahe:

hahe	hura

Maybe the arrangement is meant to depict the 4 cardinal directions. These do not have to be north, east, south, west, located in the corners of an imagined square form. The sun does not rise due north but somewhere in northeast (with the direction changing as the year advances).

... During his coronation year king Taufa'ahau Tupou IV advanced the theory that the Ha'amonga stones must have served a greater purpose than the more obvious function as a gateway. This proved the case when closer investigation revealed a secret mark on the lintel (= threshold) stone ...

On June 21st 1967 at dawn his majesty was present at this place and it was a thrilling moment when the sun rose at the exact point indicated by his interpretation of the lines etched on the great stone ...

At hahe also the ancient Mnajdra stone temple (on Malta) was mentioned. There it was the lines of the solstices which formed X.

The crosswise configuration is similar between hahe and hura, but in hahe we can see 'sun-beams' while in hura the connecting lines are like tightly drawn strings. I guess these 'strings' indicate 'nighttime', when Sun is 'absent'.

The circular forms (or rather oval - like eggs) are drawn with simple circumferences, while the crosswise henua signs in hahe presumably allude to the 'enlightened' areas (of 'broad daylight'). Inside the oval forms we cannot see - what happens inside eggs is mysterious.