Ultrix-11

I just installed Ultrix-11 3.1 using the ultrix31.tap file from https://pdp-11.org.ru/files.pl?lang=en which is the location from the comments in Stephen's Machine Room video on YouTube that I think started this thread. It installed just fine, but just like the video, I ran out of space on /usr. How can I make a larger /usr partition? Is it possible to do this at installation time? There did not seem to be an option for this. Can it be done by using an additional disk? That would seem likely, but not what a system manager back in the 70's or 80's would expect to need to do, especially as there is a relatively large amount of space left to create /user1. I noted the options for installing software using soft links to other locations. Was that the preferred method when installing additional software? Any help would be greatly appreciated. Cheers Peter Allan