|I hope that I am not too late with this – My experience is from a MK III so it also may not be entirely relevant to you, but hopefully someone finds it useful.
The floor liner goes underneath the bulkhead, and is continuous from the main cabin to the head. However, it is discontinuous, as the bulkhead sits in a groove in the liner up until the waterline. At this point, the liner disappears behind the head cabinetry and the saloon cabinetry / shelf structure. Here the tabbing begins up to the ceiling liner. In the main cabin there is a secondary liner added above the cabin seating, which is stuck on with some soft “goop” and can be carefully peeled off. It is gelcoat and one layer of glass so it is extremely thin, fragile, and bendy.
It is deceiving when you look in the portside cabin seats, as it appears that you can see the bulkhead tabbing. This is actually where the liner is tabbed in and there is also a thin sheet of plywood in the layup. I had several screws from this panel going through the main bulkhead into a trim piece on the head-side, I’m not certain whether this was done by the factory.
On the underside of the deck, the bulkhead is set in a groove in the ceiling liner with a notch cut for the chain plates. It was assembled with some structural goop as well. The most frustrating part of replacing this bulkhead for myself was removing the top of the old bulkhead. Three pieces of wood act to stabilize the very top of the bulkhead and frame the door for the head. The wood was glued on and some blind screws were used during assembly, so it required some creative use of an oscillating tool.
The other notable thing from this project is that you cannot fit a full-size bulkhead through the companionway. I contemplated replacing part of my bulkhead, but it turns out the large cabin windows are just long enough to maneuver a full-size, pre-cut bulkhead through them. Not sure if that will help you with the MkV.
I hope that this helps.