Hi,
Since the material liquifies during the process typically these proportions can be reached from what I have seen.
You can consider low-pressure injection molding since mold costs are similar.
A unique property of compression molding is that if you work with a preform, you can vary the amount of blowing agent in the preform and together with a temperature gradient in the mold, you can create foams with different densities in different areas (functionally graded foams).