UI guidelines for extensions?

[Ricardo Gladwell <ricardo gladwell gmail com>]

Hi Guys

I'm writing a Gnome Shell extension for Google Reader.

Just had a quick UI question: which part of the desktop interface would 
such an extension best belong?

At first I implemented this as a tray icon system status button, but I'm 
thinking it might be more appropriate as a panel button in the middle of 
the main panel, next to the clock?

Are there any UI guidelines as to what belongs where in the Gnome Shell 
desktop?

TIA...

--
Ricardo Gladwell <ricardo gladwell gmail com>
http://www.google.com/profiles/ricardo.gladwell
Twitter: @rgladwell - MSN: axonrg gmail com