It is always difficult to finish someone else's quilt since we have no idea what their plan was. I can't count how many quilts started one way and I changed my mind mid way or even at the end. This quilt is very "flat" and does not jump out where the tractors now get lost in the white. Even a red or black SITD could help them spring out a bit. Give a few ideas to your friend let him think on it for a bit. There is no hurry since it has been incomplete for all these year. You will get it just right. Be confident that it will be just how he envisions his mom had it in her mind .