[ccp4bb] cad, freerflag, uniqueify : free set when making anomalous from merged data

[ ccp4 6.1.13 ] [ gui 2.0.6 ] if a data set with merged Bijvoet pairs and a free set is then made anomalous - i.e. re-scaled with separated Bijvoet pairs - i do not understand how acentric reflections in the free set are extended by cad or freerflag or uniqueify. the easy question : is

[ccp4bb] Processing compressed diffraction images?

yet another compressor to consider : xz http://tukaani.org/xz/ hth