I agree with Tree climber.

But if you must cube your meat first, whynot go with some from either the back or front legs? Like a shish-ka-bob

For the marinade I use,

1/2 C soy sauce
1/4 C brown sugar
2 Tbls olive oil
1 tsp ginger
1/4 tsp pepper/
2 cloves crushed garlic

Mix well and marinate at least 2 hrs, all day is more tastefull