The body and limbs were changed entirely to the F2, and only the distinctive parts were transplanted from the Zaku Mariner.
After throwing it away and applying primer, I checked the standing balance.
The sublock gun is a bunch of junk parts because the stock and sub-grip get in the way and it's hard to hold properly.
It would probably be quicker to just scratch-make a similar weapon using reused parts without worrying about the settings.
A parallel rocket-shaped backpack in the lineage of the senior Swim Club Z'Gok.

Zaku Mariner in production | J3's Gunpla works