IMO flank is to good to mess up with marinade. Salt, pepper, garlic. Hot grill. Rare to medium rare. Slice thinly on a diagonal. Good cold also. I have two from Costco in the fridge right now.

Back on topic, I know why people like filet mignon, just not why they like it wrapped in bacon. Sort of messes up two good things. If filet is too lean for you, slather it in butter! Now that's yum!