I just installed Mahdi 2.9 on my OPO and I'm loving it, but... topic

In the button options, you can select what each hardware button actually does. I'd like to set google now (the thing where cards appear with info on things that might interest you, not the launcher) to start when I double tap the home button, but I can't seem to find it anywhere. Does anyone know how I could achieve this?

Hopefully I missed a setting somewhere and will feel really silly a few posts in, but thanks in advance!