> At the end of installboot, you get a (warning?) that the device is
  > busy. When you try a boot at the ok prompt, you get checksum failure
  > and joy departeth toward heaven.
  
  Since installboot wants to write to the raw disk device you must first
  put the system in `security level' 0. Otherwise the system will deny access.
  The canonical way to do this is to go into single user mode.

Worked a treat. many thanks. As feared by Der Mouse, SunDOS installboot fails 
because it does major,minor checks between the mounted FS and the raw device.

Thanks for the help!

-George