I will fire up a new NS7 VM and give it a go. Report back later… 
btw, the http status 500 on webtop is not necessarily because of savapage. See WebTop HTTP Status 500 - #9 by robb
/edit: quick update
I just installed your RPM… install went great. Tomorrow I will investigate further what is lacking to make the application work…
First check: savapage user is not available. When I do sudo su savapage in terminal I get the response: This account is currently not available. Looks like no shell is set for the user. https://geekpeek.net/this-account-is-currently-not-available-login-problems/
looking at /etc/passwd confirms this:
savapage:x:994:991:Savapage user:/opt/savapage:/sbin/nologin
While it should be:
savapage:x:994:991::/home/savapage:/bin/bash
(taken from manual installed server)
Also homedir is not created correctly.