The last time I went touring, many years ago, the only available cassettes were 5-speed. Combined with a double front chainwheel, this gave me 10 gears, although only 8 were actually usable (because of chain angle). In fact, as far as I remember, I only regularly used 6 of them on the tour. My question is, given that there are now 9 and 10-speed cassettes, is it feasible to go touring with just a single chainwheel? Has anyone here done that over any significant distance?