Hi fx
usually a scandoubler, doubles ONLY the Horyzontal rate to ~31.250 Hz for PAL (15.625*2) and ~31.500 Hz for NTSC (15.750*2) without touch the Vertical rate (50 for PAL and 60 for NTSC).
With a programmable FlickerFixer (like the PIV one), you may choose the Vertical rate from 50 to 120 Hz.
So, for those monitor, should be enough, to choose a rate from ~60 Hz to 75 Hz (better) for the Vertcal scan rate.
Ciao