IMHO the grip should be used for click, as that is 50x more useful, and more natural (one handed).  Then in the case where you want to drag, you can use your left hand to "sustain the click"

Then a "long" grip could mean right-click.  most anything that you need to double-click can also be right-clicked and "opened"

finally, the "push" gesture, which is somewhat awkward, could be double-click