: I will be frequently using a ferry which charges by
: the meter length of the space you use. . .

Consider cutting off the back quarter or third of the boat's length after you build it. The process is quite simple. You install a pair of bulkheads a few feet behind the cockpit. The bulkheads are separated by a little over 1/8th inch (about 3 to 4 mm) with a spacer made from cardboard or thin plywood (3mm) when they are installed. Once the glue for the bulkheads has hardened, you cut between them with a hand saw. The bulkheads themselves help guide the saw for a neat straight cut. Some sanding smooths the edges. Create a gasket with some silicone caulking compound, and bolt the two pieces of the kayak back together with bolts through the bulkheads. Most of the time you cna leave the boat assembled. But when yo are using the ferry, undo the bolts, remove the back 3 or 4 feet of the boat and shove that stern section into the cockpit. Then re- center the rest of the boat on top of your car for your trip on the ferry. Of course it helps to measure the iside of the cockpit to see how big a section it will hold before you cut anything off the tail of the boat.

You'll put a hatch on the section you are cutting off, so you;ll have a hole to access the bolts. If you put another bulkhead a few inches behind your seat, and put a hatch in that, too, you can use that area for holding lunches and gear you need to reach easily. it also serves to keep any water out of the front of the kayak should you get any seepeage from poorly tightened bolts or leaky gaskets/seals from that connection between the two parts of the boat.

There are several boat designs which are created with the intention of them coming apart into three pieces. You don;t need to go the all the trouble. Just cutting off something from the tail should save you some money on those ferry crossings, and might make storage a bit easier, too.

Hope this helps

PGJ