The GS cage is a mid cage I believe and is more road oriented. I may just have to order a cassette and give it a try. The Casseroll drivetain seems to be a mix, what with the low triple up front. It also uses brifters, so I think that may limit the derailleur choices. Harris Bicycle in Boston has a custom 13-30 cassette, expensive but I may give it a try since it appears to be design with what I want. close spacing in the high gears and some low gears at the other end. All of which are nicely spaced.