Funny you should ask. I am doing a quilt that has lots of diamonds right now. What is working for me is to cut the pieces around the diamond a quarter inch larger than the pattern calls for, then at the point end allow the side pieces to extend past the diamond about a quarter inch when I sew the seam. This does require squaring up the edges after sewing, but the diamonds are precise and have the proper seam allowance on the sides so I won't lose any points on the next step.