oops a reply to my own message, how rude :)

http://www.netbsd.org/Ports/macppc/nvedit.html also tells of
another method of delaying the boot:

""
Alternatively, you can just patch the boot-command for OF 2 and
higher systems, as such:
0 > boot-command begin ['] boot catch 1000 ms cr again 
""

I have tried it, and also 
0 > setenv boot-command begin [']..

just wanted to make clear I'm hacking blindly :)

  C.
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