I am using single thick lines. If they are diagonal they basically work with filters. If they become more horizontal or vertical, they become clipped if you apply a filter. For those, the "Flood" parameters can be adjusted so that the filter is displayed properly. See:
But if the line is completely vertical or horizontal, when a filter is applied the view is cut off completely, even when I try to adjust the "Flood" parameters.
I have tried different filters but intially want drop shadow (inner or outer) to work.
Inner drop shadow:
Outer drop shadow: