All the theory that I know says that linking two or more chopper type drivers to drive one motor will not work, so I am not inclined to even try it, although there is a school of thought that says "we won't know for sure until someone tried it". However, in your photo it appears you have not connected the motor outputs of both drivers, so only one driver will be driving the motor anyway.
I think larger motors require a larger driver, but fortunately there are many available for CNC type applications at reasonable cost which are suitable. If there was a Reprap FAQ, this would be a good question for it.
I think larger motors require a larger driver, but fortunately there are many available for CNC type applications at reasonable cost which are suitable. If there was a Reprap FAQ, this would be a good question for it.