Olympus FL36R High Speed Sync (FP Mode) how to enable on GM5?

Hi

Is it possible to get the FP mode (FP TTL Auto) working with a Panasonic GM5?

The option is not available on the flash menu when I cycle the flash's mode button (regardless of the PASM setting on the GM5).

I can't find in the manual a way to actually activate it so I am wondering if it is only available on specific camera bodies?

The GM5 restricts shutter speed to 1/50th second otherwise so might not be useful outdoors as a fill flash at this speed.

Thanks

Paul