Must have been happening with the old FD and RD and you just never noticed it. What you are describing is not caused by either derailleur. The derailleurs just move the chain onto a set cog or chain ring, and then do nothing more until you move them. Rather the path the chain takes from the top of the small cog (or 2) to the top of the small chain ring just happens to pass through the arc of the large chain ring, and thus gets caught on the teeth of said large chain ring. So I wont say don''t cross chain, I will just say get a smaller large chain ring that doesn't interfere with the chain passing from the smallest cog to the small chain ring,