Although the gladiolus makes a long line for the cascade with a single insertion, it still needs to be more filled out by adding more flowers.
Hold stems of carnations up to the bouquet and cut off a long length, allowing about an inch more for insertion.
Add another carnation on the left bottom . Stagger the lengths so it isn't perfect, but that the cascade staggers down the longer bottom.
You can see on the left side where more flowers are needed on the lower left to fill out the bouquet.
I clustered some carnations, layering one on top of the other with the flower heads facing downward.
This gives the more filled in, softly shaped like a teardrop.
Here's the final shape that I'm working towards.