When you get it right, it looks like you are falling onto rock. Before and after that area, there are areas where you can look down and see the knoll, the ramp and the balloon. But forget falling there. You have to fall onto rock to land on the grass.
It seems to me that this particular spot is hard enough to hit that it precludes making a route using it to save time. Although I am willing to try some more to get the exact pinpoint spot. I could do better with improved relations between my wiimote and my bike!
On some jumps, it seems to be important which direction your wheel is turned. I think that is probably the case with this one, too. I doubt, from experience, that you can do the drop if you start up at Hump Rock and head down.
One other thing I learned: if you pass the sweet spot going uphill and then off, you start over up by Hump Rock. If you go off even slightly downhill from the spot, you start over down below the triangle heading for the tunnel. Could it be that there are such spots right between more (or all) of the determining points (points determining where you will start over)??? Spots that, if you find them, will take you to new locations?

