Ring Flash/Macro

I just bought a DigiSlave ring flash for intraoral photography in my dental office. I can't seem to get the right shutter speed and aperature to achieve good picts. I need great depth of field and at least 80-100th/sec speed. As well I need to visualize the shot on the screen. I have tried it with sync and without. When using Manual mode at this shutter spd/aperature settings the viewing monitor is black so I can't really see what I am shooting. In Av mode at f8.0 the shutter speed registers at 1 sec and the monitor is also black but the flash goes off when the shutter button is depressed then a long lag time between pressing the shutter button and the electronic shutter activation. Any suggestions

Try the F8 flash trick;
Use Tv at 1/1000 (on the G-1 anything faster than 1/500 will be the same, on the G-2 the combination of F stop and shutter speed is incremental from 1/500 to 1/1000). The camera will shoot at 1/250 , the max synch speed, and at F8. I do not recall anyone describing this technique with a ring flash, but it should work. The faster shutter will help minimize overexposure in macros and use of the smallest apeture which will maximize dof. The reason for this strange camera limitation (we'll call it a feature today) is that the apeture and shutter are the same mechanism, and if the shutter is to move very fast it cannot open very wide.
Mike K

Yes, that will work, I found a post somewhere on the web addressing the forced synch. Past 1/640th on Tv forces the aperature to f8. Is there any way to override the aperature shutting down prior to firing?? and getting the results I need!
Thanks