DK: we'll see I got the Dreamcast BIOS farther in MESS. It issues a GDROM command, sits a while, fiddles with the interrupt enables, and then does nothing (well, actually it's running a lot of code, it just doesn't seem to go anywhere). soa-350-03 is *the* test for type 2 looping with nonzero LSA (it's actually still not exactly right in my code, but at least it's much closer).
marioman: my apologies if that wasn't you. You were the only person I knew of saying anything about the plugin and it seemed like a similar writing style.