Re: Madison River this September...
I don't think a 7' 5-wt cane rod is sufficient. That is big water with big fish and big flies and big wind. I think something like a 9', fast, 6- or 7-wt would be much better. Not that it can't be done with your 7-footer, but be prepared to be frustrated somewhat.
I haven't fished it in September, so not much help there. If it is warm and windy, hoppers and beetles can work well. Regardless, that area is beautiful; and you will have fun. Be prepared for the weather; it might be 80 degrees or you might get snowed on.