Pencil Holder

I decided I would like a cool and useful pencil holder. I printed a Gun Cylinder Pen / Pencil Holder (https://www.thingiverse.com/make:209717) but I wanted more than 6 holders. I looked at few other cool holder (https://www.thingiverse.com/thing:6476) & (https://www.thingiverse.com/thing:41703) but I decided to make a different style holder. It is configurable so you can change the all of the parameters like # of holders, # of rows, and wall thickness.

I have a attached the STL file of the holder I decided to make:
3 rows, 11 holders
2 mm thick walls, 8 mm holders

UPDATE 10APR2016:
I decide to print a larger holder to hold sharpies and pencils. The pictures and STL files are attached. I used the following settings:
3 rows, 13 holders
3 mm thick walls, 15 mm holders

I have updated the OpenSCAD file with a rotated view and defaulted the values to 15 mm holes with 3mm thick walls.

Let me know if you have any suggestions for improvements...