My experiences: Had a cut something like in Steves photo above in Malawi on the R100GS. The tyre fitted was tubeless and the first problem was breaking the bead. I then fitted the spare tube which was new but nothing special (not heavy duty). We inflated the tyre with the last of our CO2. It only lasted about 10 miles and when we dismantled it again found that the jagged adges of the original damage had rubbed through the tube - it may have helped if it had been pumped up a lot harder. Repaired the tube and turned it round and pumped it up with our knackered footpump but it didn't last long. After much messing about we got back to Llilongwe and spent a week trying to find a 17" tyre somewhere in Malawi which was an adventure in itself. We eventually had to get one flown in from Johannesburg.

Since then, I have learned from experience that tubed tyres are a slightly easier fit on the rim and that makes it easier to break the bead at the roadside and that electric pumps can be of suspect reliability so at the very least have a back up (I like C02), also some tyre lube is really useful and the inside of a badly cut tyre can be repaired using the car type mushroom tubeless repair patches with the right glue and cleaner.

In summary, to be absolutely sure you've got a 'get you home' fix for pretty much any tyre situation you need to carry quite a lot of kit.