The first rain protection has already survived three storm and decided to trust him to some.
I am glad that this time I have given this low-cost solution a chance and not a high-end product have bought the same.
FYI - I use the rain cover with a Canon 5D Mk II including battery grip, lens 24-105L and receiver for wireless remote release. A little tight it is for this combination already, but also flutters nothing. A longer lens would be no problem. I certainly 10cm "Reserve".
It will take a while - since you also do not get caught a thunderstorm every day - but these things should really wear once, I certainly suggest to again.