How many of you will change the cassette according to the ride terrain (and distance)? Our tandem has an 11-32 9-spd cassette with a 24-36-48-60 set of chainrings. This is great when we're climbing, but if I know in advance that the terrain is moderate, let's say not much over 6% I'm thinking of swapping out for something like a 13-25. Is this a common practice? Would make it a bit easier to keep up with fast singles. I'm comfortable anywhere between 80 and 100 rpm, but I don't want to go over 85 or so until my wife gets more comfortable at these higher cadences. The wider spacing on our current cassette makes it a bit difficult to find a mutually agreeable sweet spot.