The pictures are from the port hull
Not sure which panel comes out first.
Take the screws out from both sides and the one that comes out is the one.
It was that easy on the guest side so it should be the same on the owners side I would think.
The system is first rate and makes the headliner problem go away.
Loving my Lagoon
You are right
The S2 is very different
I just had a look at a 400 and there is nothing on the interior that is the same, everything is totally different,
Original 400 ceiling panels are held in place using a " tongue & groove system". The tongue is inserted into the previous panels groove & this panel is screwed to ceiling, thus providing a groove for next panel. The last panel (first one to remove) doesn't need a groove & is held in place by Velcro. Note this first panel to remove is sometimes on the outboard side of hull & sometimes on inboard side.