OK, I got the WINDOWS.nc file to work great, this is exactly how I need my own files to run. The feed rate is constant, the wheel stays tangent to the curve and there is no jerky motion. If I specify the A axis as rotational the file generates an error when it loads, so I have to leave the A axis as not rotational. Just clicking the tangential button on the settings page is apparently all I need to do. The only problem is that when I run my own files with the A commands removed, I don't get the smooth motion like the windows.nc file has. With a series of G1 X Y commands, I get a stop on each point when the wheel angle changes, so the motion is very jerky. It only appears to work smoothly with G2 commands.