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.