I have finally gotten the demensions and such for the DOTM Ratchet figure. The figure uses a mushroom joint that has a diameter of 5mm. I'm not sure if this will help you, but the mushroom joint is raised 5mm of the body. As you could probably guess, the joint is on the body, and the connection piece is in the head. Also, the original figure's head is 14mmW, 15mmH, and 13mmD. I believe that the new head should be able to fit. Thanks as always!