Thanks bunsen for reply.

I finaly figured it out.

The two slot card reader does work, probably only for one card, I havent tried two. As the mac disk controller cant mount two disks as far as I know.

The key to have it working is to format the drive, Mac Os standard for System 7 and Mac Os Extended for System 8.1.

Now I cant get my fingers on the system 8.6 in Czech localization. I have some CD but they seem to be broken, as the install allways dies half the way. System 7.5 installed no problem.