Heavy?

Two packages made from mycelium can behave very differently because “mycelium composite” is a category, not a single recipe. Particle size, fibre content, and the ratio of substrate to mycelium all change density. Higher density generally brings higher compressive strength and better edge definition, but it also increases weight and can reduce the springy cushioning that protective packaging needs.

Source: https://dirobots.com/en/mycelium-strength/