Regarding cross chaining, how much is too much?
Clearly, the advice says not to use the big/big or small/small sprocket/chainring.
But is the next biggest sprocket or next smallest sprocket OK to use?
If you have a triple, are all of the rear sprockets fair game [for the middle chain ring]?
I looked on Sheldon Brown and did some searching here but I did not find any specific answers.
(Bonus points for backing up your opinions with a reference!)