Slapping a fixed skeg on a kayak is great for following seas but if over done you may find in a stiff wind it is impossible to turn up wind and you may end up following those seas farther than you planned. Fixed skegs should be sized to eliminate weather cocking. So add a skeg and if your kayak still weathercocks in a crosswind make the skeg bigger. If it lee cocks in a crosswind (trys to turn downwind) file some of the skeg off to make it smaller. A kayak that weathercocks will abuse you. A kayak that leecocks (turns downwind) is unsafe. A wind neutral kayak will track any direction in a crosswind. In following seas a wind neutral kayak may still wallow some but it should be controllable with edging.

A quick way to trim a kayak on the fly is with a small waterbag. If you are weather cocking or tending to broach fill the bag with water and stick it under the aft rigging.

Deployable skegs or rudders can also be a sollution but it is to late tonight to go into those discussions.