I do the same thing. I don't pay for patterns. I draw them out myself. This pattern is just squares and half square triangles. For 16" block each square is 2" , 20= 2 1/2", 24"= 3", 28"=3 1/2. For each 4" you want to make it bigger you make the square 1/2" bigger.
Happy piecing and quilting!