Get the Blinky 7 for your helmet, and put the PBSF on your bike. The main LED of the Superflash is too good to have it aimed incorrectly.
This one is another option for helmet mounting -- it's on a pivot, so it's always aimed straight back, at least as long as it's not swinging wildly:
http://ecom1.planetbike.com/3010.html
And,
It'll be kinda visible... BUT, you shouldn't be crossing in such a manner that you're putting yourself at risk in the first place.