I would try adding another data series consisting of:

X value -- max x
Y value -- 0.1 and 0.16
size -- any reasonably value

Then select this series and add error bars to that series. Delete the vertical error bars, then format the horizontal error bars so that only the negative error bar shows and set it to 100%. Then set the size value to 0 to hide this second series, leaving only the negative horizontal error bar visible.