I think the issue the SanDisks I've been trying may be that they have no Hitachi controller. I don't know for sure--the product number has an H before the 512, so I was hoping that meant "Hitachi" like it does with the Pretec cards...
Someone on the Repeater List had posted a few months ago getting the Ultra II to work, but I suspect they just meant it records 4 mono tracks. If I were only doing mono looping, I might not think to check for stereo and stereo with overdub while reversed, and would think all was well with it too. (And of course, if you are a 4 channels in mono looping person, then it seems like it would be a good choice).