Thanks Darrel,

The code is working now

After experimenting, I am still confused how to adjust the x axis width, independently to left and to right from the center

The real problem is that the stick (mechanical ) stroke is not identical, say to left 30 degree, to right 26 degree
but electrically they are centered [ at 50k on 100k stick ]
this will make our curve response not equal


If we can adjust the most left / right position, then we can have nice curve, which has true equal left / right width


Jon