: The cockpit on the boat is quite small so I opted to keep the seat
: in two pieces so that I could remove it without turning it into
: a pretzel. The backrest holds the seat down.

For the same style of two piece seat -

I fasten a length of webbing at the top edge of the aft bulkhead (just below deck level) on one side of the bulkhead, over the front of the back pad, through a slotted hole in a piece of wood glued on to the keelson, forward over the sitting pad, through a female Fastex buckle just in front of the front edge of the seat pad and back via the piece of wood and over the back pad to the opposite side of the kayak from the start point. There is a block of wood in front of the seat with the male piece of the Fastex buckle on a short length of webbing. This means that by releasing the Fastex buckle, the entire seat can be removed but stops it all falling out otherwise.

Note the back pad rests against the aft bulkhead - no waste space or excess cockpit volume when emptying the cockpit during a rescue.

Alex