pxe boot.. tried with a server rent on kevworks.net, the admin tried to get it working but was not possible. I have no more details, he just said that proxmox "don't know how to handle a install this way", I think he meant proxmox starts only find local hard drivers, not finding the external machine, or whatever.
he registered here but could not open threads, then I opened it for him. I'm forwarding him the URL to try to reply here.
Regards,
Renato