Thanks everyone - I got it working.  I was misunderstanding the man pages 
and how it described the -display command.  Now I can happily run Xterms 
on both my monitors.  This system really rocks now - here's a description:

Mac IIsi
17 MB RAM
170 MB HD / 28 MB Swap partition
13" RGB color monitor
MacAvenue 15" Portrait 640x872 monitor
Python Dat Tape drive (I still can't get this one to work for some reason)

Anyhow, as soon as I get some more HD space, I could conceivable attempt 
to compile my own kernels, etc.....

thanks again, 
Dave