I personally have only seen the "strange artifacts" when using a non stock ROM. And only on a cold boot.

This has been the case with every logic board I have tested to date (except the first socketed one, which displayed the warped checkerboard pattern with the IIfx rom). I have never seen one (with good caps) that displays any kind of abnormalities like the ones talked about here with a stock ROM, and I have tried a good number of different logic boards, JDW you know that

Perhaps Larry was just like me in not finding them?

Perhaps the problems you are experiencing are caused by a failing network filter and/or scsi controller? Have you tried replacing them?