Take a piece of wood the same thickness. Mark 2" on your line of cut on top of the board. Cut to the mark. Remove board, flip over and use a square to transfer the end of the kerf to the edge of the board. Do the same with the original 2" mark on top. The distance between the two lines is what you need to hold the top cut back by.

i.e. if the bottom kerf is 2 1/2" you would stop cutting 1/2" before the end. Then finish up with jig saw or whatever.