|  With this setup, I can access raid0a as sd0a, to install boot blocks.
| [..]
|  
|  It looks like a Catch 22 to me...
|  
|  Please tell me I'm wrong!  ;-)

  No you aren't. AFAICT it is not possible with the current
tools to install a bootblock that will boot from a raid1. I
can offer you our patches for installboot along with a short
description, but that's neither mega-userfriendly nor very
nicely integrated.

	mjl