Those pens are great - dont mind going over a smooth surface either.
What do you use for the inserts???
Circles are nigh on impossible to do exactly right by hand.
I have a stencil i use - can supply these if you want, just let me know inner and outer diameters and ill send some to you - FREE! - also number required.
pics below
![](http://img117.imageshack.us/img117/6725/blacklinedetails3ze0.jpg)
![](http://img376.imageshack.us/img376/5454/blacklinedetails7qh1.jpg)