I've stayed quiet till now but here's my input from what I've seen of this rig:
The suspension may be set up fine for drag racing in controlled conditions. With the kind of power he's putting down I imagine it's been through plenty of test and tune. Problem is, it's set up like a drag car and has very very little travel and bounces wildly in uneven terrain like the ungroomed sand dunes. In those conditions it becomes clear that it wasn't designed for that, but oh well. I haven't seen him almost kill anyone and it looks like a fun ride, so have at it. The cage/chassis looks pretty underbuilt from these pics but maybe it's a work in progress in these shots like the above poster claims. It probably also doesn't weigh much more than a Rhino or RZR.