I haven't run X-Windows from the PS2 in this way. The only way which I use which works is to download and install on Windows - "xming" and "xming-fonts" (older version from the sourceforge site). Then run XLaunch, select Fullscreen, leave default display number 0, NEXT, select "start no client", NEXT, check "No access control", NEXT, FINISH. <Alt><Esc> would switch from the fullscreen X windows back to Windows if you desire.
On the PS2 I copied /usr/local/bin/win3 to win5 and changed every instance of ":0" to "my_PC_IP_Address:0", and changed the $XMODE in the sudo X line to "VESA". I then ran it as the regular user (adent) ". win5"
This starts fluxbox and displays on my PC running Windows. It is not the most secure method, so using "ssh -X" from Linux should be an improvement, I just haven't tested yet.
PS2 v9 NTSC, PS2 v12 NTSC, PS2 v15 VESA