69 Barracuda Formula S with front stock discs, A199-1 SSBC calipers upgrade disappointment

Yes, I had the same experience with them. In English we would say "they suck".

Even with a small 7/8" bore master cylinder they produced no stopping power at all. It has nothing to do with the pads or bleeding them properly. The problem is that the pistons are too small and do not provide enough clamping force. The pistons in these calipers are actually smaller than the factory Kelsey Hayes 4-piston calipers which were not that great to begin with.

I even drag raced my car with these a few times and it was an adventure trying to stop the car. I was only going 12.0 @ 111 mph in the 1/4 mile and I always had to use the last turn off. There were a few instances where I had two feet on the pedal trying to get the thing slowed down. They also wouldn't hold the car against the converter at the line so I could only launch the car from just above idle. Normal driving on the street was marginally better.

I got rid of the whole system several years ago and replaced them with Wilwoods. I would never recommend this particular SSBC system to anyone. It's a nice idea but the performance is not there. SSBC should re-design the calipers to accommodate larger pistons or just discontinue them.