Here is my take on the deck fitting.
The cup is approx 27-28mm in diameter and is built of 163g glass/200g carbon-kevlar/163g glass -weighs nothing!
The forms I used are for making chocolate candy for christmas, shown in the background.
The pin is 4mm brass tube.
The whole thing will be fitted under a hole in the deck.
I will use some type of reinforcement under the deck to spread the loads from the pin.

regards
Niklas