What Am I Doing Wrong?

I thought I'd spend a relaxing Friday arvo working on the first block of the Port De France quilt; how wrong I was! Here is the problem, and I'm hoping someone can help:

If I follow these instructions:

I get this flying goose unit; there is no seam at the top, meaning the point gets cut off...

But if I offset the triangles, I get the seam allowance, but then the unit is 1/2 an inch too short to attach to the centre square.

This pattern is one of the most odd I've worked with; all the instructions are diagrams as shown above and no written directions. Anyone have any suggestions as to what I'm doing wrong?