How full is your fuel tank?

This can give you a more approximate idea of where the leak is. If the filler neck had been cracked or broken, it would only leak a tiny amount and only if the tank was completely full. The best advice I can give you is that you drain and remove your tank and find the fuel leak. It has to be a compromise in the tank because that is the only way you could have any significant leakage into the trunk/rear wheel area.

This has something to do with hitting a woodchuck? Jesus, I can't imagine that would rupture your tank unless you already had it weakened or rusted out. I guess it got its revenge.