Hi Mario!
Welcome to Amiganews.it
There is an official backplate for Sam460ex, but it doesn't fit in the X500 Evo case, it's too high.
It has to be cut in order to close the case. Maybe I'll do the job one day, but my system do not have active fans (except the one built in the gfx card), so my AmigOne X500 Evo without the backplate can "breathe" better
However yours is
a very awesome work!
As always, I remember what you've put inside your A600
