I have been looking at the T-Bags. They have one for the GW, but have some others that will hold more. Currently riding one up and have a trip planned for the fall from Florida to New Mexico (10 days on the road).
As said above, this is a great product! Pull it off the bike and haul your stuff in the room!
I didn't get the rain liners, I just use those plastic "bags" with zippers that blankets come on. But I have never had the bag leak, even in some extended torrential rain storms.
The outside pockets are great for storing quick access items.
Here is a pic of me heading out for my 100CC ride. I stopped over in Seattle, because my daughter was flying up for her spring break. That is her helmet D-ringed to the top of the T-Bag. It also has metal rings on the sides, great for securing a CamelBak to the side, for hydration while riding.
Put over 5,000 miles last summer on the T Bag, it's great!
I didn't buy the liner, used a trash bag inside in case of rain, ran into tremendous rain in Arkansas, when I checked it that night there were only a couple of drops of water inside, and the clothes inside the trash bag were untouched.
Fantastic product. Purchased one last year before taking a 6500 mi. trip. All kinds of room and very easy to unbuckle from the bike to take with you when needed. Like the others I packed my clothing etc. in plastic bags. Rode in heavy rain in Oklahoma and everything stayed dried. Really don't think you can go wrong.