In 2004, the RAF's last Canberra accident killed 2 pilots whilst they were practising a wholly unnecessary training event - a night asymmetric touch-and-go. With no representative simulator available, it would be quite reasonable for asymmetric full stop landings and asymmetric go-arounds from above VCH, but an asymmetric touch-and-go (asymmetric touchdown, take-off again under symmetric thrust) seems like a risk too far in my view.
Oh, so wrong Beagle!
When conducting Sim Asy flight in any jet aircraft, once you've closed the throttles in the flare, you are symmetric again. An Avon at idle needed care whenever it was accelerated, but not as a function of how long it had been at idle. If you had 2 Avons that were either side of the centreline then any T&G needed care; WJ866 crashed because of what happened after it landed from the Asy approach - not before! Furthermore, the Asy GA was the real handing issue. Whilst we had to complete many of these events as BCRs, it was the latter that was always the most demanding and therefore potentially dangerous exercise, especially IMC. That said, if you handled the Canberra iaw the Aircrew Manual, it would rarely let you down.