Originally Posted by Granpa

What allows the shock shaft to move up into the shock body is the flexing of the bladder and the compression of the red sponge bushing. If that did not occur, the shaft would barely move at all. Shock action is determined by the bladder, oil, # and size of the piston holes, whether the red sponge is used, assembly technique among others.

Whether the red sponge is used depends a lot on the track surface and grip levels. It's a useful tool along with the amount of rebound you build into your shock.

Since I run mainly on low, to at best, medium grip outdoor asphalt, the default shock is a zero rebound, 3 hole piston, 40wt Losi oil, 56mm shock. For the new v2 kit, I'd start with a 57mm or so shock cause you have the droop screw.

You're wise to forget a lot of the TC chassis tuning parameters cause so much of what makes a Mini work is counterintuitive.