I myself have never used the aircraft editor in FS.  I deem it pretty much worthless, on account of it only lets you edit some of the stuff, and not everything.  If you want to do something about the flight characteristics, change the aircraft.cfg file AND the *.air file.  This will guarantee that the aircraft follows your instructions.

There are several good .air file editors out there, but AirEd is the most popular as far as I know.  You can get it here:
http://perso.wanadoo.fr/hsors/FS_Soft/fsairfile.html

I also use a spreadsheet that I got from the same site (Jerry Beckwith) that allows you to enter all the relevant data about an aircraft and then create/update *.air files and aircraft.cfg files.  Just get the flight model workbook download from Jerry's site.

Thank you for the suggestions and the guidance.  I did download the AirEd program and am now trying to understand what all the variables in the *.air file do.  Is there any sort of Help manual that explains each of the values in the *.air file?

In my attempt to change the stall speed on the aircraft, I changed the speed in both the aircraft.cfg file as well as in the *.air file under "Primary Aerodynamics/Stick Shaker Speed for Stall". This did not however make a difference on the stall speed.  Is there any other value in the *.air file that I need to change?

One last question is this: does anyone know how to change the post-stall characteristics of the plane using either of the above files?  I am trying to get the aircraft to nose-down after a stall has occurred.  Currently, the airspeed bleeds to nothing and the plane drops out of the sky at whatever attitude it entered the stall in.  Is there a way to change this?

Thanks again for all the help!