On my 2001 model PT425 I put it under the thick metal arched support for the gas tank on the left side of the engine bay. When I'd back in for the night, I'd lift the hood and plug in my trickle charger. It worked well for a while, but then one day the ears just snapped off. I figure it was not meant for high temperature areas. So, looking at one of the links provided above, i saw one made of stainless steel. That might work better for me.
Or, as you mentioned just run wires up through the tunnel and mount it on the dash, or maybe the side of the dash column somewhere would work well. I made a light bar for the underside of my canopy and fastened two lights under there so that I did not have bolts sticking up through the canopy top. I have a switchbox with four lit switches that I was going to put up there as well some day. Perhaps a lighter socket up there would be a good place for a magnetic mount rotating beacon to plug in and keep the wires out of the way.
Hmmmm.... too many projects and not enough time! :laughing: