29-3 Done once on Favela. It's surprisingly easy to get pretty high KS in Favela HC SnD.
Setup mainly was rushing with UMP Silenced and Magnum Tac Knife with Marathon Lightweight and Ninja but I also used AK-47 with Sleight of Hands Lightweight and Ninja. To get high killstreaks in this map basically make yourself be the last one every round and don't always go for the win make it last a long time. Also the best KS setup I found was Predator Emergency Airdrop and AC 130. Takes awhile to get a good game to get all 3 but if you get lucky and also have a good airdrop like I did it isn't so hard. In the airdrop I got 2 AC 130's Stealth Bomber and a Pave Low. Talk about flukey lol

^