How to hang a clothes bar across the back seat?

Naio wrote:
Any type of string, nylon strap, etc., that goes from outside to inside is going to wick water in when there's rain, and get your seat or floor wet.

You may have to cantilever off those rear hooks. Or, where do the rear shoulder belts attach?

I was thinking along the same lines, some sort of bracket strong enough to hold a metal rod. Or how about the extendable cargo rods made for pickup boxes. Don't know what it would do to the headliner though.