It's 3. I'm aware of the differences between ROM01/03 with slots, and what to choose in each case - I even tried setting the 03's slot 2 to Appletalk, and connected the cable to the modem port. Still no happy dots on the top line. But the same cable and similar setup on the 01 works fine!
Ok, got this sorted out. I have a TransWarp in my IIgs... I had tried setting the main system speed to 'slow,' but that backed it all the way off to 1MHz. What I really needed to do was to make sure it was running 'fast,' which is actually normal for the GS... the stock 2.6 or 2.8 MHz. So I needed to disable the TW, but not go too slow. I can remote boot to my hearts content now!