Update - I verified the cache setting in the SCSI2SD firmware. It was not enabled so that was not the culprit, but here's the setting to ensure this is documented for others.
In hopes of helping others I wanted to post my troubleshooting today . (OK I should be working on 'real" stuff, but the Mac is stress relief ;)
On my SuperMac accelerated SE running System 6.0.8 with my Internal SCSI2SD 5.2, the PPP Control Panel crashed the mac on "Soft Close" so that the...