Plug your PowerSpout ME directly into an Outback FM80, no other regulation needed. If you want to divert your surplus power to hot water you will need a solid state diversion relay and suitable hot water element.

Your PowerSpout ME is limited to 120 VDC maximum open circuit voltage and has a failsafe system to prevent overvoltage conditions. Connects to your FM80 in the same manner as a PV panel.

Full specifications at: http://www.outbackpower.com/products/charge_controllers/flexmax/