Thanks, Helene & Sacha.

Will bear these suggestions in mind.

Have been making great progress.

Seems the deepest extent of R. roots is 12" - after 20 years or so.

And best, in my case with soakaway concerns, to lay a large piece of
slate at the bottom of the hole to encourage upward growth of the
root-saucer.

See pic:
http://www.eskimo.com/~enumclaw/Tips...n%20Roots.html

Eddy.