Removing the spring between the VB and piston WILL NOT firm the 1-2 shift, the accumulator's cushioning effect on the 1-2 shift is strictly hydraulic i.e. as long as the piston is free to move it will cushion the 1-2 shift....spring or not. Blocking the piston simply stops the accumulator's function.

Blocker rods are typically 3" or slightly less. Tube or rod will work, the MP blocker is tubing. It's important that the blocker doesn't push the piston so far out of its bore that it keeps the VB from seating properly against the case.