[babel, ess] How can I make S-RET to be multi-session friendly?

[Mikhail Titov <mlt@gmx.us>]

Hello!

There is a wonderful post[1] on how to make S-RET to do handy things in
ESS mode. However I often find myself working on several Org documents
from different folders.

It is quite inconvenient to change a directory in =*R*= buffer each time
I work on different document.

Is there a neat way to somehow reuse Org mode property =session= that I
set buffer wide?

Also for some reason

#+PROPERTY: session *Rsomename*

does not override session name set in =org-babel-default-header-args:R=
even after =C-c C-c= on it when I re-evaluate babel code block with =C-c
C-c= on code block, while explicit block header =:session *Rsomename*=
makes difference.

,----[ snippet from dot emacs ]
| (setq org-babel-default-header-args:R
|       '((:results . "output") (:session . "*R*")))
`----

I'm running Org-mode version 7.8.10 (release_7.8.10-658-g451191.dirty)

Footnotes: 
[1]  http://www.kieranhealy.org/blog/archives/2009/10/12/make-shift-enter-do-a-lot-in-ess/

-- 
Mikhail