Using a Tandem alone, gear or not, you will need to balance the boat out. The seat / thwart needs to where the boat is in a flat position in calm water with you and your gear in it to start. Parallel to the water.
Then practice hitting some rapids, and begin taking on water inside. It should hold the water in front of you when in the rapid, but drain it quickly at the end. If you feel it takes on too much water and is too sluggish, move the seat back one notch. If not enough water, and the front is getting slapped around by waves, move it forward 1 notch.
The tandem will be slower to turn, slower to traverse and setup at the top, but when going over drops, the bow will go out a lot before it starts tilting down so will go through them and mixed up waves better.
Also, since the hull is longer, it will be tend to be faster than most everyone you are with in Solo IK's or Hardshells so you'll need to wait up more.
Eddying with a tandem is also harder because there is more water trying to force you to pivot and continue downstream for every degree off of the line of the current. You'll tend to fly by eddys others have no problem sticking in.