Heres a pic of the blue cortech tail bag the OP mentions on my blue bike (in case anybody wants to see it on a ninjette
):
I find that strapping the two back straps to the licence plate frame (right behind where the licence plate screws in), and the two front straps to the passenger peg hole work best. When I used the hooks under the back blinkers (in the picture) for the back straps, the bag kept shifting up if I hit a bump...