My wife and I have recently invested in a double kayak out here in Greece - water's lovely and warm, weather generally good, not much in the way of currents and tides, being the mediterranean, are pretty non existent. We're still trying to get lessons off the shop keeper we bought the kayak, but having difficulty making a proper rendezvous with the seller (it will come, but it takes time). To make a long story short, while the weather's so good, and the living easy, we'd like to be able to do some reasonable short trips along the coast, but, we seem to have a problem whererby we work reasonably well together while I, the man, paddle, but if my wife joins in we tend to go in circles: why? The effect is accentuated if we have a following wind/wave. It is less noticeable when I'm in front (we're about the same weight, give or take). We can still have fun, but my wife get's frustrated if she can't contribute to the paddling and is dedicated only to keeping us in a straight line.
Oh, the kayak is a DAG sit on top tribal (OK, this is only recreational, and it's to get the bug while we're in warm water!), no rudder.
I await you're comments - be gentle please!