From listening to the experts talking in the paddock on Saturday (and a bit of googling since getting home) its sounds like a proper aero car cannot use springs to control the suspension like we know it in our normal road cars (or even our JPSC cars).
If you think about it Jeffs car, with him, weighs a little over 600kg. At speed the rear wing is producing 750kg'ish of downforce (no idea what the rest of the car produces and without a moving ground plane full size wind tunnel we will never know) which is more than the weight of the car. So if you 'spring' the car for the static load it will compress a huge amount on any springs when moving. Apparently the way it is dealt with on aero cars is you effectively 'ride' on the bump stops and you fine tune the suspension setting at high speed with different bump stops. You also then throw into the equation rocker ratios and rising rate suspension but my mind started to fog over at that point
In essence the springs don't do a lot other than hold the car up in the paddock!
It maybe that the bump stops Jeff is running are now not suitable for the increased speeds (or may have just aged over the years) but ultimately the pushrod was simple not up to the load it is now expected to take. So new, stronger, pushrods will be made and fitted
Of course all the above may be complete rubbish but that's how I understood it
