mainly I noticed I need to increase glossy slightly and lower the gama on old models - not sure what filmindex does
also, it seems to affect the bumps slightly (or again they get a bit lost with the different glossy setting)
anyway - give an option for old users to use legacy settings, and I would solve my problem here with a shadow catcher, so do both

ps: can someone explain/demonstrate what the filmindex value is supposed to do in the glossy material? - I dont see obvious changes going from high to low value