>The next time you run into this please save it off and send it on over to me so I can try to see what's going on there.

See my original post for a file. You can see the error on the scaling rail when zoom in at the big end. All osnaps were on when drawing the scaling rail curve.

For the scaling rail I clicked on the top of the big end curve with a "on" osnap in perspective view, I then went to the side view and plotted the other two points and then I went back to the perspective view with another "on" osnap on the small end curve. Originally it missed both times on each end curve but mostly it misses on one of the end curves.

Perhaps I need to zoom in more when drawing my curves and the "on" osnap would work better ?

Sorry I can't post a video to explain how I did it but hopefully my text make sense.