i never understood completely what had lead sinar to make the HY6 adventure instead of going the M way further, and working here on the few shortcomings this camera has ( slow sync speed at first ). its a fantastic camera and in higher numbers i doubt it would be significant more expensive than other systems.
Yes, unfortunately the Hy6 turned out to be a strategic mistake. If Sinar really thought there was a market for 6x6 AF, they should have built a M-2 camera with square shutter and new Zeiss 6x6 AF digital lenses that could be used with either a leaf shutter or a focal plane shutter (like an AF equivalent of the Hasselblad 203 camera), similar to the concept of the Leica S2.....but with the modular concept of the M system. If they had done that, by now it probably would be the dominant MF camera in the market, possibly preventing Leica from ever getting off the ground. They could have also captured the large Contax 645 user market, if they had only built an AF mirror module for the M camera.
As far as faster flash sync, I believe Sinar did a good thing with the M camera by supplying a M-sync port in addition to the standard (slower) X-sync. The M-sync port fires as soon as the shutter begins to open. This type of sync was originally intended to trigger older flash bulbs that needed more time to reach their peak output by the time the shutter fully opens. However, you should be able to add a custom delay circuit to this port in order to sync much faster when used with electronic strobes.
I have not yet had time to test how fast this port can actually sync when a modern electronic strobe is attached to it. You may be able to get 1/500 out of it. Basically, just connect your strobes to it and keep firing with faster shutter speeds until you reach one that syncs with it. Once you know its maximum sync speed, you can use a simple timer/delay mechanism with it to control your sync speeds.