In a mixing bowl, prepare the shrimp marinade by combining the lime juice, lemongrass, brown sugar, fish sauce, oil, peppers, oyster sauce, and garlic.
Whisk the marinade and add more sugar or lime juice to your taste. Add some rub to taste.
Pour half the marinade over the shrimp and let rest for 30 minutes in the fridge.
Jicama Slaw
In a large bowl, combine the jicama and carrots.
Dress the jicama carrot slaw with the other half of the marinade and set aside to let flavors meld.
To Cook
Preheat a grill for high heat.
Remove the shrimp from the marinade and shake off the excess marinade. Thread four large shrimp, using two parallel skewers, to minimize their curling while on the grill. Apply a light coat of rub.
Grill on a hot grill for about 2 minutes on each side. Be careful not to overcook as the shrimp will get rubbery.
Mound some slaw onto an Iceberg lettuce cup. Arrange two shrimp on top. Garnish with chopped herbs and top with a lime wedge.