Lights are nice in the daytime, if only because they make you more obvious to cars. (When I'm driving I *definitely* see the bikes with "see mes" flashing in the daytime better than the bikes with no lights going)
I have a side-facing blinkie mounted where you are talking about putting your light. It seems to be a pretty good spot.
Does the bar bag have a mounting loop on the front anywhere that you could put a "see me" for your daytime rides? (the Planet Bike Superflash blinkies are amazingly bright and have a nice mounting set up)
I've also had a nice effect from putting a Mutant Guppy blinkie on the top of my helmet (feed the loop through the vent holes). It blinks in whatever direction you turn your head, so if you look at a car, you also blink directly at that car.
Oh, and if having your Ortlieb shoulder strap hanging out near your front spokes makes you nervous, you can take it off or tuck it into the bag, fold the sides of the bag in like a paper lunch bag, and then roll it down and click the closure strap. I go over enough rough pavement that I prefer to just remove the shoulder strap. But I'm a worry wart. 
Not the best picture of my Ortlieb, and its full of funny-shaped stuff, but you can see it if you squint a little:
Last edited by KnottedYet; 05-18-2008 at 07:31 AM.
"If Americans want to live the American Dream, they should go to Denmark." - Richard Wilkinson