Duotone filters based on two flood fills and the original gradient base layout.
Used the component transfer in table mode for the symmetric gradient which is not a perfect mach, but since the component transfer filter primitive is not rendered 100% correct for the "no fade" transition I assumed it would be pointless for such a fine tuning.
Maybe later if cairo will upgrade.
Anyway. This pack can easily be edited with a text editor like notepad++. Just search for the flood colour's hex code and replace them at once.
On a side note, the filter uses black and white flood fills in the process, that's why the filling tones are set red and cyan.