--snip--
>I think the legal beagles were trying
> to avoid some kind of problems if they said it was OK to convert
> straight across. No mechanical reason you can't, just legal reasons -
> it's the rules.
--snip--

I got the sense from reading the pubs that it was a loophole introduced by
omission that was then acknowledged after the fact- it's legal to convert
from R-134a because they failed to forbid it. In other words they addressed
the requirement that an R-12 system, if converted, must be converted to
R-134a and at the time just didn't address the fact that they left further
conversions wide open. I could be wrong but that's the way it seemed to me.

Robert