The next clamp will hold the gains together at the top of the #2 plank. With one hand pinch the sheer strake plank ends together where they overlap the gains of the #2 planks. Temporarily clamp the planks together. The clamp should be over the gain area in the top of the #2 plank so that it is holding the #2 planks together as well as the sheerstrake.
Loosen the bottom spring clamp just enough to slide the planks around, and push the top planks down so that their bottom edges are even with the edges of the gains. When you have them lined up to your satisfaction re-clamp them, making sure that the clamp is holding both planks.
Continue clamping the plank ends together, being careful to make sure that the gains are clamped tight and that each pair of planks is even. Don't worry too much about lining up the gains in the garboards at this point; you'll work on that in the next step. When the first stem's finished, move on to the other end. As you start clamping the second stem together, the hull will want to fold up in the middle. After a couple of the clamps are in place in the second stem end, insert a 27" stretcher near the center point of the hull to give the hull it's proper beam width. It doesn't need to be exactly in the middle, and I usually end up putting it 6" to 12" aft of the center of the hull; where ever the shape seems best to me. Once the stretcher and all the clamps are in place, you can start adjusting the clamps to align the stems.