[Double Venom]

OFM,
Have an extra person looking inside the MC wile someone steps on the brake...LIGHTLY!
If your pedal moves more than 1/4" before the person watching in side the MC sees the piston move(ing) the rod needs lengthened.

If the piston moves OR brake fluid starts to "Fountain" up immediately then there is a different problem;
Wrong MC to match you brakes;
Still air in it some where.
etc., etc., etc.
Hundreds of posts on this subject!
DV