Bowerbird - deeper negative value

Hi,
I am playing now with Bowerbird plugin and have some questions:
1. How to make negative value of deeper connection. I have some problems with my small parts and I need to have shorter indent and i can make only longer.
[IMG]http://i64.tinypic.com/rm2z4j.png[/IMG]
2. Is there any possibilty to different thickness of the material? For example i want to have middle part 2 mm and the rest 1 mm. Something like that
[IMG]http://i63.tinypic.com/28gqzh1.png[/IMG]