I marinated it for 2 and a half days. Here's the marinade;
1/2 cup (low sodium) soy sauce. 2 tbsps of honey, 3 tbsps olive oil, juice of half a lime, 7 cloves of chopped garlic, one yellow onion finely chopped, 1 teasp red pepper flakes, 1 teasp ground ginger, fresh ground black pepper.
Since it is a tough lean cut of meat, the marinade breaks it down nicely. Put it on the grill and watch closely, DON'T over cook it. (maybe even better to under cook it a bit.)
Let the meat cool and slice thin slices.
Also made some chinese cabbage with garlic,,onion, spinach and a little bit of cheese mixed in at the end. Don't know what possessed me to put some cheese on top, but it tasted real nice. Maybe it was all the recipes recently on http://www.marksdailyapple.com/ they all had cheese involved with them.
A nice glass of red wine with it topped it off. Al ready excited for left over flank steak for breakfast or lunch.
ENJOY the DAY.