I've now used the attached mod for two years (including outside winter storage). The awning has stayed dry when covered. Its also a great UV block! Obviously, this works well with my 10' awning, and you'd need to add a bit more gutter to adapt it to your awning length, but that should be fairly easy to do.
P.S. I'm rather sure this will NOT stay on for traveling (but if you try it, let me know if it works).