Thank You!
Your reply first shows that one has to take statements on the Mir site and by Canon with some grain of salt. (This is a complicated matter anyway, and that was why I asked here.) Secondly (I did not read that 430EZ manual before) necessarily setting the camera on"bulb" is not the kind of 2nd curtain operation I am expecting. I rather would like to still have controlled slow-times exposures, as in the 300TTL.

I thought of the 540EZ as an alternative to the 300TTL for those rare cases when I like to have a wide range of special effects features (high freq. strobo, 2nd curtain) in one flashlight.

I shall wait for a 540EZ to show up at the local fleamarket for cheap, and then see what to make out of it...