Oli, I’ve spoken with 2 reshapers. Both said they do not alter the core shape of the wheel to make it flat bottom. By piecing things together, it seems they strip the wheel to the core (metal?) and reapply the composite, but less so on the bottom and little more so on the sides of the bottom, and that creates the illusion the wheel is flat.
Those two and a third reshaper said you can bring your own wheel or they can help you source one for you. Control Customs were by far the most helpful of them. My wheel is there right now.
Those two and a third reshaper said you can bring your own wheel or they can help you source one for you. Control Customs were by far the most helpful of them. My wheel is there right now.