How do I change the line width on a symbol in a scalebar

[TomFlahive]

I've been able to successfully create a scalebar in code.  But I am now trying to change the line width on the scalebar.  In ArcGIS Pro, that width is changed here:

How would I make this change in code, assuming I've gotten this far:

var cimDefinition = lsaScaleBar.GetDefinition() as CIMDoubleFillScaleBar;
var cimSymbol = cimDefinition.FillSymbol1;‍‍

Thanks.