Double pie chart for warehouse stock control

Domain: drupalcommerce.
Scope: operational analysis of warehouse stocks.

Double pie chart that shows current stocks of selected products at the selected stores.
The visualisation picks the data about products ordered (for example, from checked-in orders). This data is a base for a quiery that returns current stocks at the stores. The user can select all or a part of products and stores.
Thus, information about stock sufficiency for demanded products is visualised (amount, percentage, total cost).
Double pie chart code example can be seen here: https://gist.github.com/enjalot/1262152.
Also an example of a double pie chart is attached.

The visualisation should give a clear signal about insufficiency or critical level of the stocks. These parameters should be set by the user.

UX: color picking, legends, export, etc.

NB. The visualisation is effective only for a limited range of products, not more then 20-30. For larger ranges a doubled bar visualisation can be considered.