[idvusers] Soundings from global grib file

I want to derive soundings from a global grib file.  The data source
seems OK, IDV at least offers me the option to plot a sounding.  But I
can't figure out how to specify the lat/lon, and IDV spins off until it
consumes all the memory on the Java heap, apparently in a misguided
attempt to derive a sounding for the whole world.

Similarly, how do you set the location of the probe function?  I've once
or twice gotten this to succeed, and after the plot is drawn a dialogue
appears where I can type a new lat/lon after the first random appearance
of the probe.  Am I missing a dialogue/option somewhere or what?

Kevin Havener