FWIW, I run a server with -current. That always has some small risks (which I haven't run into at all for a long time! +1 developers!!!)
Because of those possibilities, I added a second bootable backup disk. I intend to keep running -current. I will now put 6.9-stable on the second disk. This gives me both worlds. The -current I need and the 6.9-stable for safety. If you add a second disk, do a fresh install on it and copy over your files from the original disk. Now you have a working setup, no complications and a backup disk on the same machine. Sure, the machine can brick and possibly take out both disks, but a cron job can do backups to the old disk. Why do you need to use the sysupgrade utility at all? Sure, it's a handy-dandy helper, but you really shouldn't need to use it for anything. I have no doubt that you can figure out everything you need to do to avoid using it. Buy a cheap USB stick and figure out how to break it and fix it every possible way. I have little doubt that you can ask for help with that process and get answers. After you make your best effort to figure things out yourself. $ man [lots and lots of commands] Enjoy, Chris Bennett
