: Is there a point when you can have too much floatation? Does it cause the
: kayak to float up too high or affect performance in any way (apart from
: when swamped)?

Both the volume and location of the flotation will affect the stability of the boat when flooded. Basically, stability comes from the transverse inertia of the waterplane. When the boat is dry, that is based on the shape of the hull. When flooded, it is based on the shape of the bouyancy in the hull (assuming that it is fixed in place). So bouyancy added around the edges of the boat will be more helpful than bouyancy added in the center. Now there is also the effect of the water sloshing around making things worse and so probably less water in the boat is better in general. More flotation will also keep the deck edge and the cockpit coaming from going under water as easily, so you have a better chance of bailing out sucessfully. So I doubt that there is any such thing as too much buoyancy in improving the chances of being able to self rescue or keep the boat upright after flooding.