A lot of cars these days don't have the space. But, the resistance of wire running from the front to the back, and back to the front, is low enough that trunk mount should be fine as well. I haven't done it, but I've thought about it for a few my past cars.

Just one more thing to have break loose and slam into your kidneys in an accident. :P
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-IronRaven

When a man dare not speak without malice for fear of giving insult, that is when truth starts to die. Truth is the truest freedom.