Still can't see much point in fitting a servo to a 126, a good front disk conversion yes, but what advantage will you get with a servo on such a small light car?
Do you have disks fitted?
I have non servo disk brakes on my 500 which will easily lock up in the dry if I stamp on them hard enough, would a servo not just make the wheels lock up even easier but with even less feel.
If you had weak ankles or another physical reason for not being able to apply reasonable pressure to the pedal then fair enough, but for what its worth, you could end up making the car more dangerous, unless you are really thorough with you calculations, work out the required forces and use a servo that delivers the correct pressures.
A lot of race cars have the servos removed to allow for more 'feel' with out a loss of ultimate braking power.
It might be worth looking at a slightly uprated master cylinder and using braided lines to replace old flexy, make sure all the components in the whole system are evenly matched.
