Sabre IPI interface hard drives

I've recently come into ownership of some Seagate 97229 1.2GB IPI interface hard drives. I just don't have any equipment that can talk to IPI drives. So, I was hoping to be able to convert these drives to work on SMD. Since these look and seem almost identical to the CDC/Seagate/Imprimis drives that I use already, I thought it would be a simple interface board swap. Granted, I don't have any 1.2gig drives, mine are 9720 8xx mb drives. So, here's what I tried. I tried swapping both boards (with believed good boards from a dead disk 8xx drive). The main logic board from the 8xxmb drive fits just fine - one of the connectors underneath has fewer pins, but it mates up. I was hoping that this would just mean the extra heads on the HDA would simply be unused. Wishful thinking I know, but it doesn't work at all - the power supply won't come on - this must cause a dead short. So, tried swapping back the original logic and interface boards, and the drive spins up fine, comes ready and seems OK. I swapped in the control/status panel from the 8xx mb drive - this works just fine, and the one I swapped in has the full LCD and keypad - which work properly. Tried swapping just the interface boards, this time the drive displays a Fault on powerup, and while I can get it to spin like this, it never comes ready. I even tried swapping the firmware ROMs between the boards, still doesn't work. Now, I am imagining here that the incompatibilities in parts are likely because I am using boards and parts logic from a smaller drive would never work properly on a larger one, I was just hoping that it might let me use some of the surfaces. I don't have an SMD interface 1.2gb drive to try this with - so I figured I would ask - has anyone changed the interface of one of these Sabre drives before? I can't imagine how the HDA would be different between a 1.2gb IPI and a 1.2GB SMD, but you never know. I've had luck before swapping controllers between IDE and SCSI drives, and occasional luck going between drives of slightly different capacity. What machines used IPI disks? I know that an IPI controller was available for Sun3 VME based machines (of which I have only ONE). Don't see anything listed in the field guide about a qbus or unibus IPI controller. What about larger Vaxen? -Ian