I think this is one of those rare occations where the obstacle size is actually being understated. If I'm thinking of the same up, Roman, it's about armpit height and slanted at around 80 degrees. In this case there ground wouldn't allow any instantaneous power to the wheel (loamy dirt and leaves. We had enough room for a two pedal up but the approach was weird. As we started pedalling, it was slightly downhill, then just before you would normally pull up the front wheel, the ground dipped.
I figure we had two ways to approach it. Either take off early (which I think lead to Roman losing momentum when he hit it) or to try something similar to a speed jump (from BMX, you essentially bunnyhop a jump instead of launching it, that way you end up with your wheels in almost constant contact with the ground and have more speed leaving the jump) I tried the "speed jump" and managed not to smack into the rock, but I only got my front wheel to the top and without enough momentum to hook it and pull myself up. That's my challenge of the weekend.
Roman, we should have taken a picture of that.