CO2 works great to inflate the majority of the tire but use a mini pump to finish it off. I use to just rely on the CO2 but we got into distance riding which comes with multiple flats. On our last trip we changed 4 flats and rode the 5th one back 20 miles w/o any air... It sucked but it comes with the territory. At any rate, the two problems we ran into with the CO2 canister is #1 limited supply and #2 the canister piercing portion of the inflation device is rather flimsey. The first one broke imediately but unfortunately we didn't realize the issue until we had burned up two more canisters. The second device lasted longer but eventually broke. The one I currently own has lasted for years but I gently seat the canister into the inflation device now and generally pause my swearing episode until I know I haven't F'd it up. I too only carry a front tube, however, I keep it in a ziplock bag and throw some baby powder in the bag before I seal it closed. The powder helps lubricate the tube when inflating the tire and allows the tube to move when riding. My "pinch" flats have been drastically reduced since implamenting this technique. To be perfectly honest, the only time I actually put a rear tube in the rear tire is when I'm at home installing a brand new rear tire. Otherwise, it's a "trail side" front tube into the rear until I buy a new tire at the begining of the next season.
1970 FJ40- TBA