elvl vertical coordinate and gdcross

I am trying to plot data stored in the elvl vertical coordinate (taken from wrf output), and when I plot the data it plots fine, only it is upside down. I have tried a number of yaxes and ptypes, etc but the best I can get is the data plotted, only upside-down. (Reversing the values in the yaxis parameter made no difference.) Has anyone else come across this and figured out how to flip it upright?
Thank you,
Kelly Mahoney