That worked. It booted from the ERD. What does this mean, and should I proceed with a 3.9 install from here?
It means exactly what it sounds like. That big "AmigaOS ROM Update" file in DEVS: contains updates to many of the files that are in your actual, physical ROM. Device drivers, handlers, libraries, stuff like that. By Default it tries to use the versions in the file on disk instead of the ones in your (older) ROM. SKIPROMUPDATES is telling it to use the versions in the ROM rather than the newer versions on the disk.
And, yes! What the heck, at this point. Proceed! Although keep in mind you may need to edit any startup-sequences it creates (S-S is updated with each BoingBag update, also), to keep adding those two commands.
