check out
http://www.ventura-bike.co.nz/
I think I recall they are rated to something like 7kg. Now zipping two 44L Bags together would me a load of loosely packed down would overload it
If you ride solo, make sure you face the bag forward as pictured (aerodynamics of sorts). And make sure you tighten the two grip screws enough.
cheers,
Al, Australia.