Found another level loop in E3S1, which is an absolute DRAG of a level, so finding this is MASSIVE. There's a ton of tanks in it too, so doing this fast before more load in (the max I had load in was 3 in this spot) means in the tank level after, you'll only have to kill a few instead of all tanks in the level like it normally forces you to do. Hell of a skip, took FOREVER to find. It's kinda inconsistent but it DOES work and IS viable :D

To pull off, wedge behind the tree and hold DOWN while looking up and around to help you pop out. Then, turn yourself so the skinny arrow on the map is facing EXACTLY TO THE LEFT, and move UP -LEFT on your d-pad. You'll eventually walk into the exit (you'll know you are close when the BIG arrow begins to move fast)