The aileron has to be cut back all the way to front side of W25. Notice in the aileron construction detail that W25 attaches to the ribs after the cut.

Now the front of the loose aileron has to cut back to make room for the leading edge pc W26. This is also shown in the aileron detail section. The front of the aileron will have an angled cut. The two dashed/hidden lines show where to cut the top and bottom of the aileron to achieve the desired angle before glueing leading edge W26