PAM, X11, and su as a normal user?

[Steven G. Kargl]

After a few hours of frustation, it's time to ask a question.

I have 2 accounts on my machine.  I use startx to start
X11 as user kargl.  If I then su to user sgk, I cannot
fire up X clients.  For example,

troutmask:kargl[202] su sgk
Password:
troutmask:sgk[201] gnuplot
Terminal type set to 'x11'
gnuplot> plot sin(x)
gnuplot> 
gnuplot: unable to open display 'troutmask.apl.washington.edu:0'
gnuplot: X11 aborted.

I've tried using "xhost sgk@", but this doesn't work.
The only thing I can think of that may need to be
configured is PAM, but the documentation is rather
incomplete.  So, anyone know how to setup su to
permit sgk to use X clients?

-- 
Steve
http://troutmask.apl.washington.edu/~kargl/