I think we are so used to lining up the pieces that it is unnatural to offset the triangles. Have been there and have done that.
I would suggest that you start with a scrap set (same size as you have now) and just play with the alignment. Pin two sides together and then finger press them open. Do this to both sides. You will see if they fit or not and you can definitely tell which side has too much overhang. At that point, you'll know which direction to adjust.
Good luck and don't give up. Just think, you'll soon be an expert at this.