@jmnn,
You can add striplines at minimum & maximum values dynamically by using addTo method. Please refer the code-snippet below.
chart.axisY[0].addTo("stripLines", { value: minY, label: minY, thickness:2 }, false);
chart.axisY[0].addTo("stripLines", { value: maxY, label: maxY, thickness:2 });
Please take a look at this JSFiddle. for complete code.
__
Priyanka M S
Team CanvasJS