I just mounted the same Cozy hack on my RE 650.
Very little travel on the shock when jumping up and down with my 75 Kg weight. It looks like a car shock, Endurance branded which is an Indian brand, and no markings on the spring. Then again this is my first outfit, and I do not know how much wheel travel one wants on the hack?
The chair body is suspended on rubber bands, but surely there should be travel in the wheel suspension?
Is yours stiff as a board?
I am tempted to change both shock and spring, but no idea on what is an appropriate spring rate?