Obviously weight plays a role in determining how much the tire "Boepenses" (As said by the inimitable Alex Botha and quoted verbatum from WegRy
As far as wheels lifting and flex is concerned, I don't think it has anything to do with the amount of flex available. Firstly, as Michael mentioned above, I have more flex than Alex, and I lifted considerably less, and secondly, last time we were there, Alex lifted as much or more, and between the two events, we removed his front sway bar and fitted an X-link, increasing his flex from (if I remember correctly) 65 to 81.
A rear sway bar might reduce the lift on this obstacle, while a front one would theoretically probably increase the lift here, but I certainly didn't see any sign of that on Alex's car considering both performances.
My personal suspicion is that it's probably the lighter engine (yet quite torqey at the revs used here) and the body lift doing this...
Mag ons ons kenniskry met lekkerkry aanhoukry.