How to construct RigidBody2D from polygons of different mass without using joints (but with center of mass offset)?

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:bust_in_silhouette: Asked By Robotex

I can combine few RigidBody2D of different mass into one body using PinJoint2D. In this case I get correct center of mass offset that I can see in rotations, collisions and force applying.

But I want a lot of that complex objects in my game, so, PinJoint2D is too expensive in this case.

Is it possible to do the same without using PinJoint2D?