A hinge in the keel will allow a halved float to fold keeel-to-keel.

Cut each float in two near the chosen bulkhead. Laminate a new bulkhead to the part left opened for watertightness and strength. Attach the two halves with a strong hinge near keel level.

Choose one of the many alternatives to lock the half floats in position at deck level. It can be done outside the float. A webbing and ratchet like that in the kayak you indicated could work. Maybe laminate a pair of "external extensions" to the bulkheads and bolt them together.

Keep dreaming.