sync speed & telephoto lenses

I couldnt really come up with a correct title, so bear with me if you will.

Lets say my off camera flashes all sync at 1/200th, and say I'm shooting with a 70-200 2.8 non IS.

If I do venture into the 200mm range (without a tripod / monopod) I am required to keep a shutter speed of 1/320 to keep things sharp.
However, at 1/320ths, I will be getting a half black image due to the sync speeds.

Is there any way to overcome this? I cant think of anything other than reverting to using canons IR system with HSS and ettl, or tethering myself to a monopod/tripod.

Then again, I guess portraits arent usually shot at 200mm correct?

thanks

The flash stops action, within reason. So you should be able to shoot at 200mm with the flash and drop the shutter speed to your sync speed, or even lower, without much issue. I wouldn't rely on it though. Put it on a tripod for additional security.

It's only an issue if the ambient light is contributing to the exposure.

The most common situation where this issue presents itself is for outdoor fill flash using a long lens. HSS is an option, but it reduces your range. And if you're shooting at 200mm or more, you likely have some distance to the subject.

Tripods aren't usually practical for those situations, either. So your choices are to use an image stabilized lens, or work to develop a steady hand.