So I am having a hard time figuring out how to mount a tail light that is actually visible. If I use the seat post, the light will get covered up by whatever is on the rack. Seat stays are obviously covered up with the rack and panniers. I just tried rigging something up to the fender, but the road vibrations shook the light until is broke.
Please help,
scott

Mount it to the rear of the rack. Here's the one I use:

https://www.rei.com/product/776955

This.

Also, if you use a saddle bag, you can put a taillight on the back of that. Many saddle bags come with a taillight loop preinstalled. If not, you can go to the fabric store, buy some webbing, thread, and a needle, and stitch one on yourself. I hook a taillight onto the saddle bag, and then use a glue gun to glue the hook and the back of the taillight together so that it can't bounce off.

Also also, for redundancy, you can bungee a light to the back of your helmet.

Also also,

If you have a rear rack you can take a L bracket and mount it that way.That's how I did mine works good.

Here's a great thread on the topic that's just finishing up in the commuter forum: https://www.bikeforums.net/showthread...ght-Suggestion

thanks for the suggestions. The problem seems to be that not every light comes with a old school two post mount. Fortunately I purchased a Blackburn Mars light last night because it was cheap and it does come with a correct mount. Now I just need to fabricate a mount since the one that came with the rack broke when I had to modify it for a light that could not be mounted on it.

I ended up putting a light into each of the mesh pockets on the back of my panniers. I think those mesh pockets are supposed to be for water bottles, but I use them to carry cheese ... and my tail lights. The lights aren't mounted to anything, they just sit in the pocket, but the pockets are tight enough to hold them there securely.

You can get little LED lights that have an elastic loop that loops around anything and hooks back on the light, the advantage is that you can move it around and mount it just about anywhere. I mount 4 of them on the back vertical rods on my rear rack. Without a rack they work great on seat stays and things.

I fitted a Spanninga SPXb to my rear mudguard, uses 2 AAA batteries

https://www.peterwhitecycles.com/spanninga.asp