I am also thinking of the feasablity of running gas /glow with two tanks...the main tank supplying conventional 40-1 mix. A smaller tank of water/meth with maybe a metered T connection at the carb...incorporated a check valve at the water/meth(washer fluid) tank to prevent backflow. The thrust of this threefold, keeping the plug glowing...reduce costs ... and maybe a slight boost in power from the water/meth.
I suggest a stock R/C remote needle valve to meter the flow from the "aux" tank to the T connection.

Just pipe dreaming again....don't know whether the metering aspect would create it's own nightmare or whether the concept is valid...I'll try to set it up when I get time.