Been training back takes from the spin behind (name used on Ryan Hall's) back attack dvd. I am sometimes able to catch a kimura after spinning behind. It seems that this is a very common attack used by many. I've often tried defending the kimura by just forcing the elbow back to the mat. I have now started looking at a more sophisticated defense demonstrated by Kurt Osiander. It used your arm to create space between you and your opponent while the kimura is locked, and then spinning towards your elbow and pushing on your opponent's bicep for more space.
It also feel that when there is enough space, spinning the other way might be possible.