I think the proper solution may be to simply drop multitouch. Of course, this is just my bias since I find multitouch to be an awkward interface anyway. I do use the de-pinch gesture, but only because it allows me to choose the zoom level easily. I still have no idea how it chooses the point to zoom in on, so I always have to pan after the fact, whereas double-tapping doesn't require me to do that, but it zooms in some predetermined amount.