Canon was pretty open about the x100 inks and heads working fine in x000 printers but their tone is distinctly different with the x300 inks and heads. I haven't even heard of anyone doing this internally at Canon like they did with the previous generation. Nonetheless, it would be interesting to hear from someone that has drained their x100 inks and reinstalled with the x300 inks. Once the plastic teeth on the cartridges are pulled they will fit and work fine. The heads should clog but at what point and with what usage? And would a PF-05 head work or give an error message in an older printer? Seems like expensive experiments.