You can put it after the bend and aim the cutout to the side, not straight down. You could put it in the downpipe if you wanted, yes. Make sure that it won't interfere with your intake air though, so if you're getting intake air from around the engine bay, and you're dumping exhaust from the around the engine bay, you're going to have problems. See where I'm going with this..?

What do you mean by straight through exhaust?