We've done some printing on non-flat media, such as the waist line for decoration. It is very hard to work with Konica or Toshiba head, when those heads' low driver voltage, when you raise your carriage height to fit the un-flat media, set the highest point as base, the ink drop flying everywhere.
Since oce, Flora not use such high drive voltage print head, I am not sure they can handle your uneven media.
We print most on Spectra head with a driver voltage over hundred , and max height different can go to 1.8cm, anyhow, customer print most stone finishing on waist line, I am not sure what if print a face on it.. Only suggestion you can look into a high power drop dots heads...
if you like I can show you something we print on...