Bambi was tentatively lowered on to all four wheels today, and taken for a test drive. My first impression of the brakes is much better than I expected! The pedal actually feels quite soft - certainly softer than I expected: though the pedal travel is more on the road than sat in the garage. I hope as the pads and discs bed in the pedal travel will reduce.
Based on my first two miles, and all at relatively slow speeds, the brakes are good. I had one one genuine emergency stand on the brakes moment - as my next door neighbour came round an unsighted bend too fast on a single track road - there is so little traffic round here we are all guilty of doing the same. He had his wheels locked up, and I needed to slow right down to pull on to the verge, and felt quite calm about it all.
I would suggest the 22mm bore master cylinder is right for the Sierra set up. I had considered the possibility of swapping my 22mm for a 20.6mm Cortina, to reduce the leg pressure, but this is definitely not necessary, and I would not want the additional pedal travel.
It will be interesting to see what other Sportster owners feel as you start to complete your kits. GOO's initial impressions were that he was happy with his set up with a 22mm bore. Certainly based on my own experience, which is with all Ford mechanicals, I'd recommend the 22mm bore.