What if you climbed the edge and used the notches to your advantage?
You'd have to make sure there's a wide enough channel on the underside of your robot so that your components didn't get snagged on the notch, but I think it's feasible.
As for the climbing mechanism... two hooked pneumatic arms that can be rotated down onto the bars on either side of the corner of the pyramid may work.
These hooks could work in such a way that they would slide smoothly against the bars on the pyramid until they catch and hold the robot in place.
(you'd also want a really tight wheelbase)
