  The recent Auger results suggest that although coincidences of arrival
directions with 'nearby' AGN and HiRes discovery of the GZK cut-off indicate
protons, the measured longitudinal propagation characteristics indicate heavy
nuclei, if the conventional interaction model is correct. Something has to
change! Our own view is that it is possible that the AGN -implied proton
identification is not correct and that the extra galactic particles are, in
fact, mainly 'heavies', in which case the interaction problem goes away.
However, here we assume that the particles ARE protons and examine the possible
consequences. Parameters discussed include the interaction mean-free-path,
inelasticities and 'exotic' possibilities.
