UPDATE
I sent an e-mail to Planet Bike, the fender manufacturer, as follows:
I bought a set of your 45mm wide 700c Cascadia fenders last spring for one of my touring bikes. I have a dynohub on that bike and will be installing a fender mounted taillight that is dynohub powered. For that I would like to glue the power wire for the taillight inside the rear fender from near the bottom bracket back to the taillight.
I have heard a variety of suggestions for the best glue to use, but I am not hearing that anything is really very good for this.
Can you suggest the best way to run a wire inside the rear fender for my taillight?
Thanks.
Their response is as follows:
Thanks for your message. So I’m not sure what will be the best way to secure the wire within the fender. Can’t say that we really recommend affixing anything to the fender in this way and the wire has the potential of getting quite wet/dirty if it’s inside of the fender.
Sorry I don’t have a better answer for you!
Kind regards,
So, not much help. But it met my expectations, as they probably have zero experience with that topic.