If you have a top that is too small that you don't want to part with or you found one in the store that is a little bit too small that you love and you have a fabric that will go great; this project is for you :)
Take a top that is too small for you and measure the length of the seam from the seam at the tip of the underarm to the bottom of the shirt
mark the a portion of the second top/ extra material with the length wise measurements. I kind of estimated the width for me (I figured anything more than the original would fit me better-- I cut out 2-7.5x44 centimeter (3inx17in) pieces from the second fabric. you may need to finish the raw edges where the bottom will be seen
Cut the top along the seam from the seam at the tip of the underarm to the bottom of the shirt on both sides.
pin the 2 pieces of fabric to the top along the seam, with both unfinished edges facing inward.
sew along the pin line created and you are done :)