Can iPF6300 Inks Be Used in iPF6100 Printers?

From this article by Scott Martin:

Using new inks and print heads in older printers

In the past, users of Canon’s older printers have been able to install Canon’s newer inks and print heads without any repercussions. All users had to do was flush out their old inks using the “Move Printer” function, pull the plastic teeth on the new cartridges and install them normally. While the new x300 cartridges can physically fit and be installed in the same way, Canon discourages people from doing so because the new ink formulation with finer pigment particles and increased polymer will clog older head designs. The new PF-05 heads found in the new x300 printers are custom tailored for these new inks and aren’t compatible with the older printers.