I have a standard arcade cabinet with standard arcade monitor and it runs a std Jamma game (SF2') without issue.
I tried the Soft15kHz but i cannot get it to display the single image, just the dbl-screen that JPAC uses protect the monitor from higher frequencies. i have tried this with an old Riva TNT2 and a GeForce MX2 400.
I have also tried using the QuickRes utility to change the resolution to all the possible combinations (16bit) by the same issue, two copies of the same image on the screen. If i remove the jumper from the 30kHz option then i do not get sync at all.

Any help out there?