I can deal now with 1/200 but when panning is not possible (motorcycle coming towards you for example) and just want fill flash to kill shadows i get some blur where the flash is not hiting the subject so i have to dismiss using the flash... and here is where the sync of the hassy opens some doors...
Even the hassie that syncs at 1/800 (correct me if im wrong) woudnt serve you too much in that situation.
For example: you set your lights to do a fill flash, that means low output flash is normally done, 1/1500 to up, you sync your camera to 1/800, one part of the "thing" will frozen to 1/1500 another to 1/800, the ghost image is still there.
So, in best of cases you will have to check your lights if you can go to 1/800 and still do a fill light, some systems have velocity control but i think that if you want that low velocity output you have to power up your unit pretty hard, and that reminds too much light to do a fill flash.
So after encountering with those problems time before, my only advice is light subjects perfectly, the easiest way is on camera flash, ringlight and pretty frontal kind of lightind, if you want backlight or side lighting do it accurately!!