Well, after much research and deliberation, I finally picked up my tankbag. I was very hesitant about purchasing a bag without trying it on, due to the plastic fairings surrounding our gas tanks, but I picked a real winner. The FirstGear tankbag fits beautifully and has the luxury of having both magnets and suction mounts to swap between.
The bag cost me right at $105, which wasn't bad due to the size and excellent build quality. I have tried a number of different positions arranging the bag on the tank, and the best fit came with using the 2 rear magnets at the metal/plastic joint of the tank and flipping the front 2 magnets underneath the tank bag and latching them to the bung. There is also a front strap I latched around the tree and tightened. All in all, she ain't going anywhere.
The absolute best part of the bag is being able to unzip the main portion, leaving the smaller section still latched to the tank. Very freaking cool feature and really easy to get off and on.
I have yet to take her out on the street, but I have no doubt that she'll do just fine. I'll keep this thread updated once I have a road test.