So thanks to some recommendations in another thread, I got a new saddle, but now I have a new quandry. I want to attach my rear blinky to it.

My old saddle had some springs and extra rails that made a good place to zip tie the blinky, but my new saddle just has the two parallel rails running the length of the saddle. I want to attach the blinky to the saddle because if I attach it to the post it will be hidden by the trunk when I have the trunk on it.

I have another light (not as bright but it does have turn signal blinkers a brake indicator and an attached horn and was a gift from my wife so I don't want to get rid of it) on my rack, so I can't put it there. Just looking for ideas on how best to firmly attach it to the seat. My last zip-tie attachment job looked ok in the apartment, but after the second or third bump had the light drooping and eventually facing straight down (not much use for safety on the ride.

Any suggestions?

Hate to ask the obvious, but there's no way to just attach it to the trunk when using the trunk? My rack trunk has a little loop on the back for a blinkie to attach to. I aslo installed a bracket for my rear blinkie on the back of the rack. Would those be options for you?

You know, I feel like an idiot for not looking to see if I can use the clip on the blinkie (planet bike superflash, I think) when I have the trunk on and the post bracket when it's not. I'll have to look to see if there's something I can clip it to on the post. Maybe I'm overdoing things since I ziptied another bracket for another of the same blinkie to my helmet, but I just want to make sure I'm visible. I do have that (not so useful but can't get rid of because my wife thinks the turn signals are essential) light already on my rack and I don't really have room for another because of where the fenders are and panniers attach. If I used the rack/panniers all the time I'd be fine just permanently attaching the light to them, but this is my one bike for everything so I want to ride without them but with the light sometimes.

I have one PBSF attached to my saddle above my seat bag, I just wrapped 1" wide double sided velcro strips around the saddle post, then have a single 6" long velcro strip that the PBSF is clipped too. It's not pretty, but it works, can be angled correctly, and is quick to pull off if I need to lock the bike in public. I'm sure there are much more elegant ways to attach it...

As an alternative, I've been thinking about attaching the one bracket to my seatpost and buying a second bracket to ziptie to the clip where I attach the shoulderstrap to my trunk. That way, I always have one bracket exposed to slip the light in.

I've seen other people just use a strip of velcro around the seatpost and clip them on that. Mine nicely clips to my rack.

You could mount it to the left seatstay. Always stays on the bike that way and you can visually check to be sure it's blinking.

mine goes on the back of the trunk. most trunks have some attachment point just for this purpose! :-)

this is not mine but came up in a search:
https://www.jandd.com/detail.asp?PRODUCT_ID=FRRPII

or how about an adapter to attach it to the rack itself?
https://www.rei.com/product/776955

I used some angle aluminum from the Home Depot to make a custom bracket which bolted to the rails p-clamp style.

I mount a 2nd off my left drop bar

bubblegum.

I had same problem so I got a frame wedgie thingy instead. Kept the seat post available for the blinkie and the frame wedgie thingy is also easier to get into while riding.

I get round this by attaching the blinkie to the straps on the back of my helmet

I do have a blinkie that I've ziptied to my helmet. With that, this one, and the weaker one on my rack (and my reflective vest), I should be visible at night. Should be a bit of overkill even, but just want to be safe and all that given a cyclist was killed a couple of blocks from my house (wasn't a visibility issue, but still it made me paranoid).

I did find a way with added rubber to get the smallest bracket to attach to the seat rail (and still allow fitting of my seat pack when I'm not running full trunk/pannier setup), so thanks for all your suggestions.