It seems that 'with filledcurves' ignore lw parameter - code below give me different results on gnuplot 5.0.7 and 5.2.1 (cygwin) - see attached files. When "x1" is removed - line is plotted thicker (as expected) albeit result is not what i want to accomplish.
set style fill transparent solid 0.5 border
plot "file" using 1:(100-\$8) title "busy" lw 2 lc rgb "red" axis x1y1 with filledcurves x1
Pijoter
From the documentation: