Guncon2 with arcade CRT H+V Sync

[toastboy]

I've got an old arcade cab with mame+mister connected via KVM switch.

Both mame+mister output separate H+V sync to the hantarex crt in the cab.

The guncons I think need composite sync. What's the best way of supplying this without messing up the sync to the display?

Obviously combining H+V wires will give me composite sync to the guncons, but I suspect that will upset the CRT's display.
Or will it? Perhaps the hantarex could cope with composite sync?

Or maybe it's possible to isolate the sync using a diode on both H+V wires, before they are combined. In that way sync to the monitor remains separate, but the diodes conduct H+V into a combined sync for the guncons, without upsetting the CRT?

I'll test any attempts using a throwaway video card on a PC before the mister of course. Old ATI cards that support 15khz are easier an cheaper to find than a new de-10.

[FoxbatStargazer]

Another approach should be to turn on/ovr the SoG switch, connect the green cable from Mister I/O to the guncon, then apply a sync stripper between the guncon and monitor. Or if its free, you can use direct video on the HDMI side to your monitor while having the I/O just push SoG to the guncon.