Yeah, I don't think any 030 PDS card is going to officially allow a slot C or D configuration with the jumpers. The jumper configuration should tell the card both what address range to respond to, and which IRQ line of the 030 PDS slot to use, and hopefully this is some GPIO pins read by an onboard controller, because that'll pretty much be doom. So, hacking the card(s) will be necessary to be able to configure it to use a different slot, in order to get more cards working.
One ray of hope is the MacCon+30iET64 supposedly supports being configured as slot E (according to the SE/30 minitower page), which won't work on an SE/30, but it seems the IIsi's video doesn't use slot E, so all would be good. So if you got that working in slot E, you'd have 4 pseudo-slots in use?
If your MacCon allows configuring as slot E, and it doesn't work, that might be worth further investigation to figure out why.
Reading the IIsi dev notes, it seems it had 4 IRQ lines on the 030 PDS, not the 3 I had initially thought on the SE/30. Presumably the 4th is the slot E's IRQ line, which is in use on the SE/30 but not on the IIsi. So, 4 pseudo-slots doesn't seem unobtainable on a IIsi. Does the 3rd edition of the Guide to ... Hardware cover the IIsi? If so, the VIA and 030 PDS chapter might have some insight.
One ray of hope is the MacCon+30iET64 supposedly supports being configured as slot E (according to the SE/30 minitower page), which won't work on an SE/30, but it seems the IIsi's video doesn't use slot E, so all would be good. So if you got that working in slot E, you'd have 4 pseudo-slots in use?
If your MacCon allows configuring as slot E, and it doesn't work, that might be worth further investigation to figure out why.
Reading the IIsi dev notes, it seems it had 4 IRQ lines on the 030 PDS, not the 3 I had initially thought on the SE/30. Presumably the 4th is the slot E's IRQ line, which is in use on the SE/30 but not on the IIsi. So, 4 pseudo-slots doesn't seem unobtainable on a IIsi. Does the 3rd edition of the Guide to ... Hardware cover the IIsi? If so, the VIA and 030 PDS chapter might have some insight.