LelandJT

^It's gotta be mentioned that shifting under load is asking for a broken chain with any derailleur system. The modern systems, especially electric, can do it but you are putting massive side loads on the links. I've also seen bent cassette cogs from shifting under load. If you get practiced with it you can say "shift" and both ease off the power briefly enough to do a clean shift without losing appreciable momentum. Half a pedal stroke is all it takes and it helps if you plan the shift before your cadence gets bogged down.

Didn't mean to hijack your thread but as a mechanic on tandem tours I have seen the carnage and had to explain this many times.