The parts of the base seats are cured and could be assembled.
Test fit:
TAF replied that the back channel 6 is replaced by a thicker channel 25, but what is the orientation and how is the piano hinge attached (new question out to TAF):
The pins don’t go through the holes in the brackets, I need to check this with TAF as well:
And the adjustment mechanism needs solid riveting, but I only have a 2X rivet gun and a hand squeezer and both a not strong enough for these larger solid rivets: