Finally had some time to look into this.
Now Trust LCD 1300VA (via COM) and existing Server1 (Debian Squeeze / ISPConfig3 and Webmin working like a dream. (Webmin installed long time back as per older tutorial....
nut core-part was installed/configurated as "standalone" as per earlier totorial link (if you use, look also comments as done for earlier verson...)
To answer my question about nut-cgi Google found for me easy way with webmin beta-module "nutd" (i.e. no need for www-client / site in ISPConfig)
Perfect Server one step more perfect (for me)
I'll assume that when done like this minimal security issues to consider....