[Tom Wells]

classical,

Maybe you took care of this, maybe not?

Your car's rotors may have a layer called "glaze" due to deposition of the prior pad material. If this isn't removed by a light turning or maybe some emery cloth, you may find the car won't stop well no matter how high the braking line pressure.

A layer of glaze definitely has a lower coefficient of friction.

I'd suggest looking at this before trying other sized cylinders.

Just another possibility...

Tom

PS: It looks like the front rotors were turned? If so, you could still check the rears. If they're OK then maybe do what Bob proposed.