  We have previously explored cylindrical packings of disks and their relation
to sphere packings. Here we extend the analytical treatment of disk packings,
analysing the rules for phyllotactic indices of related structures and the
variation of the density for line-slip structures, close to the symmetric ones.
We show that rhombic structures, which are of a lower density, are always
unstable i.e. can be increased in density by small perturbations
