When you say rear calipers do you mean that the pistons could be seized or there could be air trapped at the rear??
I just wound the rear pistons in no problemo when i changed the pads so they are not seized and there is no air trapped there?
Maybe on the focus this is normal?
It frustrates me as i have driven many cars where the brake pedal is hard a a rock and very reassuring

P.S i remember why i chose DOT 5.1, in the technical guides that Stu at M Developments produced, it stated that DOT 5.1 had the highest boiling point and there was nothing really negative said about using it apart from having to change it at more frequent intervals??? Im now worried DOT 4 will feel even worse? And its definately DOT 5.1 i have been using not DOT 5