One plus on the Cortech, you can get the side saddlebags as well. I have the tail and side bags, check the pics from the skyline trip and you'll see them on the Raven.
One negative, the "rain proof" is a cover that comes with the bag, it is not waterproof without covering it, but I haven't found many that had built in rain proof, most use some kind of cover.
The tail bag is bungee, so you can bungee all the way under, or shorten them up and bungee to the hand rail. I've ridden off a couple of time forgetting to strap them and have not had it fall off, the pad under it grips the seat well.
thread with pics:
Our Skyline Drive (VA) ride WITH PICS AND VIDS!
I had a cooler on one side for all our drinks/lunch. They are huge.