I'd say so. If you look at the sample Portal 2 Bindings [1] the labels on the bottom seem to pointing underneath the controller and in the disassembly image [2] there seems to be another button-looking piece in front of the bottom portion.

[1]: http://cdn2.store.steampowered.com/public/images/promo/livin... [2]: http://cdn2.store.steampowered.com/public/images/promo/livin...