Thanks for the feedback guys.
I am actually using a Zone VI cold light head on another enlarger already, but I never got to control contrast well enough - whether with pyro or Rodinal negatives.
I tried Joe Englander's additive set of Rosco filters suggested by Anchell on his Variable contrast printing manual:
#3107
#389
#3304
#3315
#3313
#3308
#3202
#68

Beside the fact that #3313 and #3308 are light magenta, which doesn't really look additive, the spacing between the grades look pretty odd.

SoI just bought a whole Rosco swatchbook and I will try with different shades of blue and green. Or maybe go to split print directly.
Has anybody tried a better set?

gm