ROS driver configuration, mech characteristics

I'm currently looking at the ROS driver for Roboteq motor controllers. It uses the G command to send the desired speed to the motorcontroller. The ROS driver receives these commands from the cmd_vel topic which is typically in m/s (for the linear velocity) and rad/s (for the rotational component around the Z axis of the robot) for a differentially driven robot. These are sent directly to the motor controller without any conversion. This would seem to suggest that the conversion to each individual wheel speed happens on the motorcontroller which would require the mech characteristics as are shown in roborun+. I'm unsure how to put the controller in an operating mode where it makes use of these mechanical characteristics to calculate the required velocity of each wheel. Mixed-mode seems to be the closest but this doesn't account for the robot's mechanical characteristics and represents the velocities as two numbers (-1000 to 1000) which are related to the motor's maximum speed.

Perhaps the intention is that users would perform the conversion to the mixed-mode type commands by modifying the ROS driver based on their own robot but I just wanted to check I wasn't missing something, especially since the mech characteristics are listed in Roborun+ and I can't really see what they're used for.

Thank you for any help you can provide