Don, I'm moving to SF..
Mark can stay home. No need to wake the dragon...
actually Mark Bourne was one of the first people I thought of for you that is capable of handling your (Matthias) space with the capability that the site deserves and release the potential that is there. However, I need to check my geography of the US.. is not Mark closer to LA?
For you Matthias, in addition, to bring the third part of the equation to fruition, one of the important things that had crossed my mind for your design was that I hope you have seen Marc Keane's 'Tiger Glen Garden' that is featured on the Front Page of JGO http://japanesegardening.org/
The reason being that you would benefit by deciding an intellectual idea that becomes your 'courtyard' garden.
The front of your garden is then a prologue that sets up the dialogue in the courtyard. A four sided sculptural living painting per se`. (diorama?)
(and, green ground cover is not out of the question.. there are solutions.)
The same goes for Pauls' garden, except we need to figure out the dialogue that already exists. Most small spaces would benefit from this idea, rather than pre-deciding about materials and then cooking up an idea to suit, yet, it can also be done.
I'll go wake Mark up edzard (I'm still waiting for some other replies, unless they have directly contacted Matthias themselves)