Originally Posted by operator
I don't get why. You have one tooth difference and it's a measley 10 gear inch difference on a 52 chainring from 12 to 11. Anyways to answer your question, the same query has been posted in the road cycling forum not too long ago.
I have compact so it will be 50 up front. Anyway only thread I found was: Digging my 11-27 "custom" Dura-Ace cassette! So I'm guessing it kind of answers my question you can mix and match. Although I'm not sure how he kept the 19th cog. Since last three are connected together.