KDE2 X display security

[Ross Boylan <RossBoylan@stanfordalumni.org>]

If I open a terminal and su, I find I'm unable to open additional
displays (e.g., 
su
emacs &
).

If I change to a regular terminal and do xhost + then the emacs & as
root works.

I know the install script says it's shutting down remote access, but
this is local access.  I tried removing -nolisten from
/etc/X11/kdm/Xservers (I'm using kdm), without effect.

What's the right knob to tweak so that I can do the su; emacs & thing?

A related question: Through the menu I can get System | Terminal
(Super User Mode).  The result comes up as root, and I can pop open
additional displays.  But it's not a very good root, because it still
has my path as a regular user.  Is there a way to fix this?

Thanks.