Originally Posted by
speedevil
This should work, unless you're intentionally exceeding the recommended chain wrap capacity. Some derailleurs will allow their stated capacity to be exceeded, others don't.
I would just caution you to shift into the big chainring, and carefully work your way up to the big cog in the back, checking that the chain length allows that combination without exploding.
+1 except I always check that not only can I carefully get into the big-big, I can do it aggressively like I might when I hit the top of the big climb and I am completely stupid (until I recover a little oxygen). (Wrecked RDs run much less satisfactorily than slightly too-loose chain.)
Ben